WO2023184415A1

WO2023184415A1 - Transimpedance amplifier having filtering function

Info

Publication number: WO2023184415A1
Application number: PCT/CN2022/084603
Authority: WO
Inventors: 王永
Original assignee: 华为技术有限公司
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-10-05
Also published as: CN118891822A

Abstract

The present application relates to the technical field of chips and discloses a transimpedance amplifier having a filtering function, for use in enabling the transimpedance amplifier having the filtering function to be small in occupied area, low in complexity, and low in power consumption. The transimpedance amplifier is of an open-loop structure and comprises a differential input end and a differential output end, the differential input end comprising a positive input end and a negative input end, and the differential output end comprising a positive output end and a negative output end. A first amplification circuit and a first load are coupled to a first signal path where the positive input end and the negative output end are located, a second amplification circuit and a second load are coupled to a second signal path where the negative input end and the positive output end are located, and a first amplifier is coupled between the first amplification circuit and the second amplification circuit; the first amplification circuit is used for controlling current flowing through the first load; the second amplification circuit is used for controlling current flowing through the second load; and the first amplifier is used for improving the filtering characteristic of the first signal path and improving the filtering characteristic of the second signal path.

Description

A transimpedance amplifier with filtering function

Technical field

The present application relates to the field of chip technology, and in particular to a transimpedance amplifier with filtering function.

Background technique

The traditional RF receiving chain includes circuits such as Low Noise Amplifier (LNA), Mixer, Low Pass Filter (LPF) and Variable Gain Amplifier (VGA). . With the development of technology, the increase of functions and the improvement of integration, the pursuit of low-power radio frequency receiving links has always been the direction of research.

Among the commonly used methods, the number of amplifiers can be reduced by reducing the order of filters in the radio frequency receiving chain, thereby saving power consumption. Alternatively, a Transimpedance Amplifier (TIA) and LPF can be combined to save the number of amplifiers. For example, LPF can use a 2-stage TIA, but it requires two amplifiers, and the radio frequency receiving link is usually a total of two in-phase (in-phase, I) links and a quadrature (quadrature, Q) link, referred to as I path and Q path, so there are a total of 4 amplifiers in the RF receiving chain. The amplifier consumes a large amount of static power, which is not conducive to reducing the power consumption of the entire link. Moreover, in this method, the signal bandwidth of each filter in the LPF is determined by resistors and capacitors. For radio frequency receiving links with lower bandwidth, resistors and capacitors will occupy a considerable area, which is not conducive to cost reduction.

Contents of the invention

Embodiments of the present application provide a transimpedance amplifier with a filtering function, which can be implemented with low area, low complexity, and low power consumption.

In order to achieve the above objectives, the embodiments of this application adopt the following technical solutions.

In the first aspect, a transimpedance amplifier with a filtering function is provided. The transimpedance amplifier has an open-loop structure and includes a differential input terminal and a differential output terminal. The differential input terminal includes a positive input terminal and a negative input terminal. The differential output terminal includes a positive output terminal. terminal and negative output terminal. The first signal path where the positive input terminal and the negative output terminal are located is coupled with a first amplification circuit and a first load; the second signal path where the negative input terminal and the positive output terminal are located is coupled with a second amplification circuit and a second load. A first amplifier is coupled between an amplifier circuit and a second amplifier circuit; the first amplifier circuit is used to control the current flowing through the first load; the second amplifier circuit is used to control the current flowing through the second load; the first amplifier , used to improve the filtering characteristics of the first signal path, and to improve the filtering characteristics of the second signal path.

In the transimpedance amplifier with filtering function provided by the present application, the first amplification circuit and the second amplification circuit can stabilize the currents at the positive input terminal and the negative input terminal of the transimpedance amplifier, so that the gain of the transimpedance amplifier is equal to the current multiplied by the current. Based on the resistance of the first load (or the second load), adjusting the gain of the transimpedance amplifier on the first signal path by changing the resistance of the first load, and adjusting the transimpedance amplifier by changing the resistance of the second load Gain on the second signal path. Moreover, through the first amplifier, the filtering characteristics of the transimpedance amplifier can be improved, for example, to exhibit second-order filtering characteristics, thereby realizing a transimpedance amplifier with filtering effect. In addition, the transimpedance amplifier with filtering function provided by this application occupies a smaller area, has lower complexity, and lower power consumption.

In one possible design, a first amplification circuit and a first load connected in series are coupled to the first signal path where the positive input terminal and the negative output terminal are located; the first amplification circuit includes a first amplifier circuit connected across the first switching device. capacitor, a second capacitor, and a first current source coupled to the positive input terminal; a second amplification circuit and a second load in series are coupled to the second signal path where the negative input terminal and the positive output terminal are located; the second amplification circuit includes a transverse The third capacitor and the fourth capacitor are connected to the second switching device, and the second current source is coupled to the negative input terminal.

When the open-group amplifier is used in a radio frequency receiving link, the radio frequency receiving link includes two parallel links, I and Q, with the phase difference between I and I being 90 degrees. The circuit structures of the I path and the Q path are the same, that is, the circuit structures of the second signal path and the first signal path are symmetrical. Moreover, in this application, the first amplification circuit, the second amplification circuit and the first amplifier occupy a smaller area, the number of amplifiers is also reduced compared with the existing technology, and the power consumption is reduced.

In a possible design, the first terminal of the first switching device is coupled to the first terminal of the first load, the second terminal of the first switching device is coupled to the positive input terminal, and the first terminal of the first switching device is coupled to the first terminal of the first load. A first capacitor is connected across the second end of a switching device, a second capacitor is connected across the second end of the first switching device and the third end of the first switching device, and the first output end of the first amplifier is coupled to the second between the first terminal of the capacitor and the third terminal of the first switching device, and the first input terminal of the first amplifier is coupled between the positive input terminal and the first terminal of the first current source;

The first terminal of the second switching device is coupled to the first terminal of the second load, the second terminal of the second switching device is coupled to the negative input terminal, and the first terminal of the second switching device and the second terminal of the second switching device span A third capacitor is connected, a fourth capacitor is connected across the second terminal of the second switching device and the third terminal of the second switching device, and the second output terminal of the first amplifier is coupled between the first terminal and the second terminal of the fourth capacitor. between the third terminal of the switching device, and the second input terminal of the first amplifier is coupled between the negative input terminal and the first terminal of the second current source; the second terminal of the first load and the second terminal of the second load are coupled; The second terminal of the first current source is coupled to the second terminal of the second current source.

That is to say, the first amplification circuit in this application includes a first switching device, a first capacitor and a second capacitor, which are used to stabilize the current flowing through the first signal path. Compared with the current stability controlled by resistors and capacitors in the prior art, the area occupied by capacitors and resistors is greatly reduced. Moreover, compared with existing transimpedance amplifiers with filtering functions, the circuit structure of the present application has low complexity.

In a possible design, the first current source is used to generate a first quiescent current, and the first quiescent current flows through the first load, so that the gain of the negative output terminal changes with the change of the resistance of the first load; the second current The source is used to generate a second quiescent current, and the second quiescent current flows through the second load, so that the gain of the positive output terminal changes as the resistance of the second load changes.

In this way, when there is no signal input into the transimpedance amplifier, that is, no signal current is generated, the gain of the transimpedance amplifier can be equal to the quiescent current multiplied by the load resistance while the quiescent current at the input end of the transimpedance amplifier is stabilized. This allows the gain of the transimpedance amplifier to be adjusted by changing the value of the load resistor. When there is a signal input, the first amplifier circuit and the first current source can also control the stability of the signal current on the first signal path, so that the gain of the negative output terminal on the first signal path changes with the change of the resistance of the first load. Just change. The gain changes on the second signal path are the same.

In a possible design, the second capacitor and the first switching device generate a first pole, the first load and the first capacitor generate a second pole; the fourth capacitor and the second switching device generate a third pole, and the second load and the third capacitor produces the fourth pole.

In a possible design, when the first capacitor is connected across the first terminal of the first switching device and the second terminal of the first switching device, a first zero point of the feedforward is generated; the first amplifier is used to control the first zero point of the feedforward. The position of the zero point is at a high frequency, so that the first signal path has a second-order filter characteristic; when the third capacitor is connected across the first end of the second switching device and the second end of the second switching device, a feedforward is generated the second zero point; the first amplifier is used to control the position of the second zero point at high frequency, so that the first signal path has second-order filter characteristics.

Therefore, when poles and zeros are paired and one zero can offset one pole, this application uses the control of the first amplifier to push the position of the zero away, and the offset effect of the zero will not occur, and at high frequency, causing the transimpedance amplifier to exhibit second-order filtering characteristics.

In one possible design, the transimpedance amplifier also includes a voltage stabilizing circuit, which is used to form negative feedback and control the voltage at the positive output terminal and the voltage at the negative output terminal to be consistent with the reference voltage.

This design takes into account that once the gain required for the circuit is determined, the purpose is to keep the voltages at the positive and negative output terminals constant. Taking the first signal path as an example, at this time, the voltage at the negative output terminal can be kept constant by adjusting the current on the first signal path. However, once the voltage at the negative output terminal changes, it will affect the working range of the second-order TIA (transimpedance amplifier with filter function) circuit. When the second-order TIA receives a large signal, such as a large current signal at the positive input terminal, the The signal will be compressed or not processed properly. However, while adjusting the current on the first signal path, the transconductance of the first switching device will also change with the current. Therefore, this application can add a voltage stabilizing circuit on the basis of the transimpedance amplifier with filtering function provided in the first aspect to form negative feedback and control the voltage of the positive output terminal and the voltage of the negative output terminal to be consistent with the reference voltage.

In addition, since the first load and the second load are connected in parallel in the second-order TIA circuit, quiescent current does not flow into both ends of the first load, and quiescent current does not flow into both ends of the second load. There is no voltage drop across the second load, and without voltage drop it will not offset the voltage margin.

In a possible design, the voltage stabilizing circuit includes a third switching device and a fourth switching device coupled in series, and also includes a second amplifier; a signal path where the third switching device and the fourth switching device are located, and a first load and a third switching device. The signal path where the two loads are located is coupled in parallel between the positive output terminal and the negative output terminal; the output terminal of the second amplifier is coupled between the gate of the third switching device and the gate of the fourth switching device; the first terminal of the second amplifier The input terminal is coupled between the first load and the second load coupled in series, and the second input terminal of the second amplifier is used to input the reference voltage.

A second aspect provides a radio frequency receiving device, which includes a transimpedance amplifier with a filtering function as described in the first aspect or any possible design of the first aspect.

A third aspect provides a chip, which includes the radio frequency receiving device as described in the second aspect.

A fourth aspect provides a communication device, which includes the chip described in the third aspect.

It can be understood that any of the radio frequency receiving devices, chips, communication equipment, etc. provided above can be applied to the transimpedance amplifier with filtering function provided above. Therefore, the beneficial effects it can achieve can be referred to the corresponding The beneficial effects of the method will not be repeated here.

These and other aspects of the present application will be more clearly understood in the following description.

Description of drawings

Figure 1 is a schematic structural diagram of a traditional radio frequency receiving link provided by an embodiment of the present application;

Figure 2 is a schematic circuit diagram of a 2-stage TIA with LPF provided by an embodiment of the present application;

Figure 3 is a schematic circuit diagram of a TIA provided by an embodiment of the present application;

Figure 4 is a schematic circuit diagram of a transimpedance amplifier TIA with filtering function provided by an embodiment of the present application;

Figure 5 is a schematic circuit diagram of a transimpedance amplifier TIA with filtering function provided by an embodiment of the present application;

Figure 6 is a schematic diagram of a TIA frequency response curve with filtering function provided by an embodiment of the present application;

Figure 7 is a schematic diagram of a 2-stage TIA circuit provided by an embodiment of the present application;

Figure 8 is a schematic diagram of a 2-stage TIA circuit provided by an embodiment of the present application;

Figure 9 is a schematic diagram of a 2-stage TIA circuit provided by an embodiment of the present application;

Figure 10 is a schematic diagram of a 2-stage TIA circuit provided by an embodiment of the present application;

FIG. 11 is a schematic structural diagram of a system chip provided by an embodiment of the present application.

Detailed ways

To facilitate understanding, some descriptions of concepts related to the embodiments of the present application are provided for reference. As follows:

LPF: Remove unnecessary high-frequency components from the input signal and remove high-frequency interference.

TIA: It is a type of amplifier. The amplifier type is defined according to the type of its input and output signals. In the electrical field, assume that the amplifier gain A=Y/X, Y is the output and X is the input. Since a signal is represented by either voltage or current, there are four types of amplifiers combined. For example, when the input X is a current signal and the output Y is a voltage signal, A can be understood as having the dimension of resistance.

VGA: It is a key module in the radio frequency reception (ReceiveX, RX) link. The automatic gain control circuit composed of a feedback loop provides constant signal power to the analog-to-digital converter (Analog to Digital Converter, ADC). When analog circuits need to amplify or attenuate signals, this function can be implemented by VGA. VGA plays a vital role in the analog front-end of the wireless communication receiver/transmitter. The VGA at the fundamental frequency compensates for the gain attenuation of the RF module and IF module. And the VGA amplifies the output signal to the amplitude required by the ADC.

LNA: When a weak signal is amplified, the noise of the amplifier itself may seriously interfere with the signal, so it is hoped to reduce this noise. The LNA is an amplifier with a very low noise figure. It is generally used as a high-frequency or medium-frequency preamplifier for various types of radio receivers (such as WiFi modules in mobile phones, computers, or iPads), as well as amplification circuits for high-sensitivity electronic detection equipment.

Amplifier (AMP): especially an instrument that uses transistors or tubes to amplify electronic signals.

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Among them, in the description of the embodiments of this application, unless otherwise stated, "/" means or, for example, A/B can mean A or B; "and/or" in this article is only a way to describe related objects. The association relationship means that there can be three relationships. For example, A and/or B can mean: A alone exists, A and B exist simultaneously, and B alone exists. In addition, in the description of the embodiments of this application, "plurality" refers to two or more than two.

Hereinafter, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of this embodiment, unless otherwise specified, "plurality" means two or more.

As shown in Figure 1, the traditional RF receiving chain includes circuits such as LNA, Mixer, LPF, VGA, local oscillator (LO) and ADC. Among them, the LNA can superimpose the RF signal obtained by low-noise amplification of the signal received from the antenna and the mixed signal output by the LO and output it to the Mixer; the Mixer down-converts the received superimposed signal to an intermediate frequency and outputs it to the LPF. ; LPF filters the received intermediate frequency signal, removes high-frequency interference, and outputs the high-frequency-removed signal to VGA; VGA amplifies the received signal and provides constant signal power to the ADC; ADC Perform analog-to-digital conversion on the signal, and output the resulting digital signal to other modules of the radio frequency receiving link for processing, such as output to the processing module for processing.

For this radio frequency receiving link, pursuing a low-power receiving link has always been a research direction. Among the commonly used methods, the number of amplifiers in the link can be reduced by reducing the order of the filter. The number of amplifiers here refers to the number of amplifiers in the LPF. The 2-stage TIA shown in Figure 2 is a design of LPF. It is understandable that two amplifiers are needed in this 2-stage TIA. Considering that the radio frequency receiving chain usually includes two channels, I and Q, if Figure 1 shows one of the I or Q, the two channels There are four amplifiers in the LPF, and the amplifiers consume a lot of static power, which is not conducive to reducing the power consumption of the entire radio frequency receiving link. Moreover, although this solution adopts a closed-loop structure and has good linearity, a certain gain control can be achieved by changing the resistance in the second-order TIA, but the implementation is more complicated. In addition, in this solution, the signal bandwidth of each amplifier in the LPF is determined by the resistors and capacitors in the LPF. For a low-bandwidth radio frequency receiving link, the resistors and capacitors will occupy a considerable area, which is not conducive to cost reduction.

Figure 3 shows the structure of another TIA, which adopts an open-loop structure, and the power consumption is reduced compared to the TIA with a closed-loop structure. Among them, inp and inn are two current input terminals, outn and outp are two voltage output terminals, and Vref is a reference voltage input terminal. The TIA shown in Figure 3 can achieve common mode control and increase the output impedance. The power consumption of the TIA has nothing to do with the signal bandwidth, and lower power consumption can be designed. However, in the TIA shown in Figure 3, the input impedance is the reciprocal of the transconductance of the NMOS transistor 31 and NMOS transistor 32 at the input end. If the input impedance is designed to be too low, the input current of the TIA needs to be increased, and the power consumption will increase. Therefore, the input impedance cannot be designed too low. Moreover, the TIA shown in Figure 3 has no filtering function but only a signal amplification function. If there is no filtering function, when using the TIA shown in Figure 3, it is necessary to design a second-order or higher filter in the subsequent stage of the TIA. The overall power consumption of the radio frequency receiving link system is not reduced. In addition, this solution requires a common-mode stable amplifier 33, which also adds additional power consumption.

Therefore, this application proposes an LPF circuit design to address the problems of large power consumption, high cost, and high complexity in the design of LPF in the radio frequency receiving link. This application designs a circuit for LPF that can simultaneously realize the TIA function of a second-order filter, in order to reduce the power consumption, cost and area of the LPF.

The transimpedance amplifier with filtering function provided by this application can be applied to the LPF of the radio frequency receiving link. The radio frequency receiving link includes two parallel links, I and Q. The phase difference between I and I is 90 degrees. The circuit structures of the I path and the Q path are the same, and the embodiment of this application introduces the circuit structure of one of them.

It should be understood that the radio frequency receiving link can be used in radio frequency receiving systems, which is suitable for both high-bandwidth systems, such as WiFi, and low-bandwidth and low-power consumption systems, such as Bluetooth (BlueTooth, BLE) systems.

In some embodiments, the radio frequency receiving link can be used in a radio frequency transceiver chip. The radio frequency transceiver chip can be used in terminal equipment and network equipment, for example, and can also be used in other equipment that can transmit and receive signals. This application does not limit it.

In the transimpedance amplifier with filtering function provided by the present application, by coupling a first amplification circuit between the positive input terminal and the negative output terminal, and coupling a second amplification circuit between the negative input terminal and the positive output terminal, the transimpedance amplifier can be The currents at the positive and negative inputs are stable, so that the gain of the transimpedance amplifier can be adjusted by changing the resistance of the load in the case where the gain of the transimpedance amplifier is equal to the current times the resistance of the load.

In this process, through the coupling relationship between the first amplification circuit, the second amplification circuit and the first amplifier, the filtering characteristics of the transimpedance amplifier can be improved, for example, it can exhibit second-order filtering characteristics, thereby realizing a transimpedance amplifier with filtering effect. The transimpedance amplifier with filtering function provided by this application occupies a smaller area, has lower complexity and lower power consumption.

The transimpedance amplifier with filtering function provided by this application is introduced below.

As shown in Figure 4, this application provides a transimpedance amplifier TIA with a filtering function. The TIA has a switching structure and includes a differential input terminal and a differential output terminal. The differential input terminal includes a positive input terminal inp and a negative input terminal inn. The output terminal includes a positive output terminal outp and a negative output terminal outn.

A first amplification circuit and a first load are coupled to the first signal path where the positive input terminal inp and the negative output terminal outn are located, and a second amplification circuit is coupled to the second signal path where the negative input terminal inn and the positive output terminal outp are located. circuit and a second load, a first amplifier AMP1 is coupled between the first amplification circuit and the second amplification circuit;

The first amplifier circuit is used to control the current flowing through the first load;

The second amplifier circuit is used to control the current flowing through the second load;

The first amplifier AMP1 is used to improve the filtering characteristics of the first signal path and to improve the filtering characteristics of the second signal path.

In some embodiments, the first load and the second load are resistors.

Therefore, in the transimpedance amplifier with filtering function provided by the present application, the first amplification circuit and the second amplification circuit can stabilize the currents at the positive input terminal and the negative input terminal of the transimpedance amplifier, thereby increasing the gain of the transimpedance amplifier. Based on the current multiplied by the resistance of the first load (or the second load), the gain of the transimpedance amplifier on the first signal path is adjusted by changing the resistance of the first load, and the gain of the transimpedance amplifier on the first signal path is adjusted by changing the resistance of the second load. The gain of the transimpedance amplifier on the second signal path. Moreover, through the first amplifier, the filtering characteristics of the transimpedance amplifier can be improved, for example, to exhibit second-order filtering characteristics, thereby realizing a transimpedance amplifier with filtering effect.

In this way, compared with the transimpedance amplifier with filtering function provided by this application, the signal bandwidth of the filter is determined by resistors and capacitors in the prior art. For systems with low bandwidth, capacitors and resistors occupy a considerable area. This application Through the coupling of the first amplification circuit, the second amplification circuit and the first amplifier, a transimpedance amplifier with filtering function can be realized, which occupies a smaller area, has lower complexity and lower power consumption. Moreover, the number of amplifiers required in a single I or Q path is smaller than in the existing technology. For example, in the filter circuit of Figure 2, a single I or Q path requires two amplifiers. In the filter provided by this application, a single I Channel or Q channel only requires one amplifier, and the power consumption is low.

In some embodiments, referring to Figure 5, the first amplification circuit and the first load in series are coupled to the first signal path where the positive input terminal inp and the negative output terminal outn are located, and the first load is connected in series with a resistor. R1 shows; the first amplification circuit includes a first capacitor C1 and a second capacitor C2 connected across the first switching device M1, and a first current source S1 coupled with the positive input terminal inp;

The second amplifier circuit and the second load in series are coupled to the second signal path where the negative input terminal inn and the positive output terminal outp are located. The second load is represented by a resistor R2; the second The amplifying circuit includes a third capacitor C3 and a fourth capacitor C4 connected across the second switching device, and a second current source S2 coupled to the negative input terminal inn.

In the following description, the first load is the first resistor R1 and the second load is the second resistor R2.

Referring to Figure 5, for the first signal path, the first terminal a of the first switching device M1 is coupled to the first terminal b of the first resistor R1, the second terminal c of the first switching device M1 is coupled to the positive input terminal inp, and the first terminal c of the first switching device M1 is coupled to the positive input terminal inp. The first terminal a of a switching device and the second terminal c of the first switching device M1 are connected across the first capacitor C1, and the second terminal c of the first switching device M1 and the third terminal d of the first switching device M1 are connected across There is a second capacitor C2, the first output terminal e of the first amplifier AMP1 is coupled between the first terminal f of the second capacitor C2 and the third terminal d of the first switching device M1, and the first input terminal of the first amplifier M1 g is coupled between the positive input terminal inp and the first terminal A of the first current source S1.

When the first signal path and the second signal path are symmetrical, referring to Figure 5, for the second signal path, the first terminal h of the second switching device M2 and the first terminal i of the second resistor R2 are coupled, and the second switch The second terminal j of the device M2 is coupled to the negative input terminal inn. The first terminal h of the second switching device M2 and the second terminal j of the second switching device M2 are connected across a third capacitor C3. The second terminal j and the third terminal k of the second switching device M2 are connected across a fourth capacitor C4, and the second output terminal l of the first amplifier AMP1 is coupled between the first terminal m of the fourth capacitor C4 and the second switching device M2. between the third terminal k, and the second input terminal n of the first amplifier AMP2 is coupled between the negative input terminal inn and the first terminal B of the second current source S2;

The second terminal o of the first resistor R1 is coupled to the second terminal p of the second resistor R2;

The second terminal C of the first current source S1 and the second terminal D of the second current source S2 are coupled.

Among them, in the radio frequency receiving chain, the positive input terminal inp and the negative input terminal inn are coupled with the two output terminals of the mixer Mixer, and are used to receive the current output by the two output terminals of the Mixer.

The negative output terminal outn and the positive output terminal outp are used to couple with the two input terminals of the VGA or ADC of the subsequent stage.

The switching devices in this application, such as the first switching device, the second switching device, the third switching device and the fourth switching device involved in this application, may be MOS transistors, specifically PMOS or NMOS, etc.

From the circuit structure of FIG. 5 , it can be understood that both the first current source S1 and the second current source S2 can provide a stable current, and the stable current can be understood as the quiescent current required by the TIA with a filtering function. In this way, the input end of the TIA can be made to have low impedance. When there is no signal current input to the positive input terminal inp and the negative input terminal inn, the stable current generated by the first current source S1 flows through the first resistor R1, the stable current generated by the second current source S2 flows through the second resistor R2, and the negative output The gain output by the terminal outn is the stable current generated by the first current source S1 multiplied by the first resistor R1, and the gain output by the positive output terminal outp is the stable current generated by the second current source S2 multiplied by the second resistor R2. In this way, the gain of the TIA can be adjusted by changing the resistance values of the first resistor R1 and the second resistor R2.

In other words, the first current source S1 is used to generate a stable first quiescent current, and the first quiescent current flows through the first resistor R1, so that the gain of the negative output terminal outn changes with the change of the resistance of the first resistor R1. The second current source S2 is used to generate a stable second quiescent current. The second quiescent current flows through the second resistor R2, so that the gain of the positive output terminal outp changes with the change of the resistance of the second resistor R2.

When there is a signal current at the positive input terminal inp and the negative input terminal inn, due to the negative feedback effect of the first amplifier AMP1, the voltage of the positive input terminal inp and the voltage of the negative input terminal inn will also be stabilized, so that they flow through the first signal path The signal current of the first resistor R1 and the signal current flowing through the second resistor R2 of the second signal path will also be stable. Under stable first quiescent current, second quiescent current and stable signal current, the current flowing through the first resistor R1 of the first signal path is stable, and the current flowing through the second resistor R2 of the second signal path is stable. This application can adjust the gain of the TIA by changing the resistance values of the first resistor R1 and the second resistor R2.

According to the TIA with filtering function provided in Figure 5, in terms of filtering function, on the first signal path, the second capacitor C2 and the first switching device M1 will generate the first pole, and the first resistor R1 and the first capacitor C1 will A second pole is generated, forming a second-order filter. Since the first capacitor C1 is connected across the first signal path, a feedforward zero point will be formed. However, due to the feedback effect of the first amplifier AMP1, the current flowing through the first signal path and the second signal path can remain unchanged, so that there is always a gain with TIA, and the zero point is always at a high frequency. The zero points do not cancel the poles, and the TIA still exhibits second-order filtering characteristics. Therefore, a TIA with a filtering function can maintain the second-order filtering characteristics well while changing the gain.

Among them, the zero point can be understood as, when the signal input amplitude of the TIA is not zero and the input frequency causes the TIA output to be zero, the input frequency value is the zero point. The pole can be understood as, when the input amplitude of TIA is not zero and the input frequency makes the output of TIA infinite (TIA stability is destroyed and oscillation occurs), this frequency value is the pole. Poles can be used to suppress noise, and zeros can be used to worsen noise. The poles and zeros are in pairs, and a zero cancels a pole. This application uses the control of the first amplifier AMP1 to push the position of the zero point away, and the offset effect of the zero point will not occur, and at high frequencies, the TIA still exhibits second-order filter characteristics.

Here is an example. In some embodiments, for the first signal path, when the transconductance gm of the first switching device M1=100u and the capacity C2 of the second capacitor C2=4pf, FIG. 6 shows the configuration of the present application. The TIA frequency response curve of the filter function includes curve 1, curve 2 and curve 3. The horizontal axis represents the frequency of the signal received by the TIA with filtering function from the mixer, in Hz, and the vertical axis represents the gain on the first signal path in the TIA with filtering function, that is, the current value on the first signal path and The voltage value obtained by multiplying the resistance of the first resistor R1 is in V or dB, and dB is the gain in decibels.

Referring to Figure 6, curve 1 corresponds to: the capacity C1 of the first capacitor C1 = 4pf, the first resistor R1 = 5K; curve 2 corresponds to: the capacity C1 of the first capacitor C1 = 2pf, the first resistor R1 = 10K; curve 3 corresponds to: The capacity of the first capacitor C1 is C1=1pf, and the first resistor R1=20K. Among them, when the first resistor R1=5K, the gain of TIA when receiving signals is about 74V; when the first resistor R1=10K, the gain of TIA when receiving signals is about 80V; when the first resistor R1=20K, when TIA receives signals The gain is approximately 86V.

It can be seen that the greater the value of the first resistor R1, the greater the gain of the TIA. By changing the value of the first resistor R1, the gain of the TIA at the negative output terminal outn can be adjusted. Similarly, the gain adjustment for the second signal path is similar to that for the first signal path.

In addition, for the filtering characteristics of TIA, for the first pole in the first signal path, the position of the first pole is determined by the capacitance C2 of the second capacitor C2 and the transconductance gm of the first switching device M1. When the value of gm When the values of C2 and C2 remain unchanged, the position of the first pole remains unchanged. For the second pole in the second signal path, the position of the second pole is determined by the resistance of the first resistor R1 and the capacitance of the first capacitor C1. When the values of R1 and C1 remain unchanged, the second pole The position of the pole remains unchanged.

When the position of the first pole and the position of the second pole remain unchanged, the bandwidth of the TIA remains unchanged. Referring to Figure 6, when the frequency of the current signal received by the positive input terminal inp remains unchanged, for example, when the frequency is 10 ³ Hz, after the current signal passes through the first signal path, when the resistance of the first resistor R1 is increased, the negative The gain of the output terminal outn increases from 74V to 84V. In this way, the TIA's gain can be changed while keeping the TIA's bandwidth constant. When the frequency of the current signal is less than or equal to 10 ⁶ Hz, curve 1, curve 2 and curve 3 are flat curves, that is, in the frequency range where the frequency of the current signal is less than or equal to 10 ⁶ Hz, the gain of the TIA can be changed. At the same time, the bandwidth of the TIA remains unchanged, and the signals in the frequency range less than or equal to 10 ⁶ Hz are amplified through the gain and output to the subsequent module, such as VGA.

When the frequency of the current signal is greater than 10 ⁶ Hz, the gain of the TIA decreases sharply. The current signal with a frequency greater than 10 ⁶ Hz is attenuated. The signal with a frequency greater than 10 ⁶ Hz cannot be output to the TIA's subsequent module while achieving gain amplification. . In this way, the TIA with filtering function provided by this application maintains the second-order filtering characteristics while changing the TIA gain.

Compared with the 2-order TIA solution provided in Figure 2, when the LPF of this application uses a TIA with 2-order filtering characteristics, one amplifier is required in one of the I or Q channels, and a total of 2 amplifiers are required in the I and Q channels. The number of amplifiers is reduced and power consumption is lower. Moreover, the circuit implementation is relatively simple and the circuit occupies a small area. Compared with the TIA provided in Figure 3, it not only provides a signal amplification function, but also has second-order filtering characteristics. This application does not need to design an additional second-order or higher filter in the subsequent stage, and the TIA provided in Figure 3 does not have filtering characteristics. This application Reduce the overall power consumption of the RF receiving circuit.

For the 2-stage TIA provided in this application that can provide stable current, the stable current provided by the first current source S1 and the stable current provided by the second current source S2 can control the current input terminals (inn and inp) of the TIA through the reference voltage vref. voltage, and at the same time generate the quiescent current required by the TIA through the reference voltage vref, that is, the first quiescent current and the second quiescent current mentioned above. When the first amplifier AMP1 is used to form negative feedback, the current input end of the TIA can be made to exhibit low resistance. When the gain of the TIA is equal to the small signal current multiplied by the load resistor (R1 and R2), the gain of the TIA can be adjusted by changing the value of the load resistor.

Referring to Figure 7, the 2-stage TIA provided in Figure 7 is another implementation of the 2-stage TIA circuit provided in Figure 5 of the present application. Figure 7 shows two amplifiers AMP11 and AMP12, as well as resistors R11 and R12. One input terminal of the amplifier AMP11 is used to input the reference voltage vref, and an input terminal 61 and an output terminal 62 are connected across the first switching device M1 An input terminal of the amplifier AMP12 is used to input the reference voltage vref between one terminal d and the positive input terminal inp. An input terminal 63 and an output terminal 64 are connected across one terminal k of the second switching device M2 and the negative input terminal inn. One end of the resistor R11 is coupled to the positive input terminal inp, the other end is coupled to the resistor R12, and the other end of the resistor R12 is coupled to the negative input terminal inn. In actual implementation, the amplifiers AMP11 and AMP12 in Figure 7 and the resistors R11 and R12 can be replaced by AMP1, the first current source S1 and the second current source S2 in Figure 5.

Specifically, taking the first signal path as an example, the present application can input the reference voltage vref to an input terminal of the amplifier AMP11. The ratio of the reference voltage vref to the resistance of the resistor R11 is the first quiescent current on the first signal path. When the magnitude of the reference voltage vref remains unchanged, the first quiescent current remains unchanged. When the first quiescent current remains unchanged, the common mode voltage of the positive input terminal inp can be designed to be lower, and the switch size of the mixer Mixer coupled to the positive input terminal inp can be designed to be lower, thereby reducing the area occupied by the device.

When the 2-stage TIA receives a signal from the mixer Mixer, the positive input terminal inp will receive the signal current, and the positive input terminal inp will generate a voltage. When the voltage of the positive input terminal inp rises, the amplifier AMP11 will compare the reference voltage vref and The voltage difference at the positive input terminal inp is amplified. When the amplified voltage difference is input to the input terminal of the first switching device M1, the first switching device M1 will generate a voltage to suppress the voltage rise at the positive input terminal inp, so that the reference The voltage difference between the voltage vref and the positive input terminal inp decreases, which will eventually make the reference voltage vref and the voltage of the positive input terminal inp the same, making the signal current of the positive input terminal inp fixed. In short, the first switching device M1 will form negative feedback, causing the positive input terminal inp to exhibit low resistance. In other words, when the signal current input from the positive input terminal inp flows through the first signal path to the first resistor R1, the first signal The path is a low resistance path. In this way, by controlling the voltage value of the reference voltage vref of the amplifier AMP11, the voltage value of the positive input terminal inp can be controlled, so that the voltage value of the positive input terminal inp is stabilized, so that the voltage value flowing through the first signal path to the third signal path is stabilized. A small signal current in resistor R1 is stable. Furthermore, the gain of the second-order TIA can be adjusted by changing the resistance of the first resistor R1 on the first signal path.

Similarly, by inputting the reference voltage vref to the amplifier AMP12 on the second signal path, the voltage of the negative input terminal inn can also be controlled to stabilize the small signal current of the second resistor R2 on the second signal path, thereby achieving adjustment. The resistance of the second resistor R2 is used to adjust the gain of the second-order TIA.

Similar to the explanation of the filter characteristics given in Figure 5, the 2-order TIA shown in Figure 7 also has 2-order filter characteristics.

In addition, in the 2-stage TIA shown in Figure 5, when the circuit of the 2-stage TIA does not receive a signal from the mixer, if human factors or deviations during chip production cause the resistance of the first resistor R1 to change, The voltage at the link common mode point (negative output terminal outn) of the second-order TIA will change with the resistance of R1. However, once the gain required for the circuit is determined, the goal is to keep the voltage value at the negative output terminal outn unchanged. At this time, the voltage of the negative output terminal outn can be kept constant by adjusting the first quiescent current on the first signal path. Once the voltage of the negative output terminal outn or the positive output terminal outp changes, it will affect the working range of the second-order TIA circuit. When the second-order TIA receives a large signal, for example, when the positive input terminal outp receives a large current signal, the signal will are compressed or cannot be processed normally. However, while adjusting the first quiescent current, the transconductance gm of the first switching device M1 will also change with the first quiescent current.

Therefore, this application also provides a circuit architecture of a 2-stage TIA, as shown in Figure 8. This application improves on the circuit of Figure 4.

Based on the circuit architecture of Figure 4, the transimpedance amplifier also includes a voltage stabilizing circuit, which is used to form negative feedback and control the voltage of the positive output terminal outp and the voltage of the negative output terminal outn to be consistent with the reference The voltage vcom remains consistent.

In some embodiments, as shown in Figure 9, the voltage stabilizing circuit includes a third switching device M3 and a fourth switching device M4 coupled in series, and also includes a second amplifier AMP2;

The signal path where the third switching device M3 and the fourth switching device M4 are located and the signal path where the first load R1 and the second load R2 are located are coupled in parallel between the positive output terminal outp and the Between the negative output terminal outn;

The output terminal q of the second amplifier AMP2 is coupled between the gate of the third switching device M3 and the gate of the fourth switching device M4; the first input terminal t of the second amplifier AMP2 is coupled between Between the first load R1 and the second load R2 coupled in series, the second input terminal of the second amplifier AMP2 is used to input the reference voltage vcom.

Specifically, referring to Figure 9, the output terminal q of the second amplifier AMP2 is coupled between the first terminal r of the third switching device M3 and the first terminal s of the fourth switching device M4, and the first input terminal of the second amplifier AMP2 The coupling t is between the second terminal o of the first resistor R1 and the second terminal p of the second resistor R2, and the second input terminal of the second amplifier AMP2 inputs the reference voltage vcom;

The second terminal u of the third switching device M3 is coupled to the second terminal v of the fourth switching device M4; the third terminal w of the third switching device M3 is coupled to the first terminal b of the first resistor R1. The fourth switching device M4 The third terminal x is coupled to the first terminal i of the second resistor R2.

It can be seen from the 2-stage TIA shown in Figure 9 that the second amplifier AMP2, the third switching device M3 and the fourth switching device M4 form a negative feedback circuit, which is used to make the output voltage of the negative output terminal outn and the positive output terminal outp equal to the reference voltage. vcom remains consistent.

Specifically, the first resistor R1 and the second resistor R2 are connected in parallel to the circuit, and negative feedback can be formed through the second amplifier AMP2 and the third switching device M3 and the fourth switching device M4, so that the output common mode voltage of the TIA is always maintained. At vcom, or in other words, the voltages of the negative output terminal outn and the positive output terminal outp of the TIA are always maintained at vcom. In this way, even if the first resistor R1 or the second resistor R2 is switched, or the resistance value of the first resistor R1 or the second resistor R2 is changed, the output common mode voltage of the TIA remains unchanged.

When the negative output terminal outn and the positive output terminal outp are inconsistent with the reference voltage vcom, the second amplifier AMP2 can amplify the voltage error. The output terminal of the second amplifier AMP2 outputs current to the third switching tube M3 and the fourth switching tube M4. After the switch M3 is turned on, the current flows through the first resistor R1. After the fourth switch M4 is turned on, the current flows through the second resistor R2. The voltage at the second terminal o of the first resistor R1 is compared with the reference voltage vcom. , the voltage at the second terminal p of the second resistor R2 will also be compared with the reference voltage. When it is determined that there is a voltage error after comparison, the second amplifier AMP2 will continue to amplify the voltage error and output it. In this way, under the action of the negative feedback of the second amplifier AMP2, the voltage of the second terminal o of the first resistor R1 and the voltage of the second terminal p of the second resistor R2 will be consistent with the reference voltage vcom. In other words, the voltages of the negative output terminal outn and the positive output terminal outp are consistent with the reference voltage vcom.

In addition, since the first resistor R1 and the second resistor R2 are connected in parallel in the 2-stage TIA circuit, the first quiescent current does not flow into both ends of the first resistor R1, and the second quiescent current does not flow into both ends of the second resistor R2. current, there is no voltage drop across the first resistor R1 and the second resistor R2, and no voltage drop will offset the voltage margin.

In the second-order TIA circuit provided in Figure 5, both the first resistor R1 and the second resistor R2 have static current flowing through them, and there will be a voltage drop, which reduces the working range of the second-order TIA circuit.

According to the further explanation of Figure 7 to Figure 5, this application also provides a 2-stage TIA circuit as shown in Figure 10. Figure 10 can be understood as a 2-stage TIA circuit obtained by combining Figures 7 and 9.

Therefore, through the second-order TIA provided by this application, compared with the number of amplifiers required by the second-order TIA provided in Figure 2, the number of amplifiers required by the second-order TIA provided by this application is reduced, and the power consumption on the link is reduced. And the bandwidth control has changed from pure resistance and capacitance control to transconductance gm (such as M1) and capacitance (such as capacitance C1 and C2). Compared with the area occupied by resistors and capacitors, switching devices such as MOS tubes and capacitors occupy a smaller area. Small. Moreover, compared with the TIA provided in Figure 3, the second-order TIA provided by this application also has a filtering function and is less complex.

The embodiment of the present application also provides a system chip. As shown in Figure 11, the system chip 110 includes: a processor and a transceiver. The transceiver may include, for example, an input/output interface, pins or circuits. The circuit may It includes the radio frequency receiving link in this application, and the radio frequency receiving link includes the transimpedance amplifier with filtering function in this application. The processor executes computer instructions. Optionally, the transimpedance amplifier in any of the radio frequency receiving links provided in the above embodiments of the present application may be included in the transceiver.

Optionally, the system chip may also include memory.

Optionally, the memory is a storage unit within the chip, such as a register, cache, etc. The memory may also be a storage unit located outside the chip in a communication device (such as a terminal device or network device), such as a read-only memory ( read only memory (ROM) or other types of static storage devices that can store static information and instructions, random access memory (random access memory, RAM), etc. Among them, the processor mentioned in any of the above places can be a CPU, microprocessor, ASIC, etc. The processor and the memory can be decoupled, respectively arranged on different physical devices, and connected through wired or wireless means to realize the respective functions of the processing unit and the memory, so as to support the system chip to implement the above embodiments. Various functions. Alternatively, the processor and memory may be coupled on the same device. It should be understood that the processor in the embodiment of the present application can be a central processing unit (CPU for short), and the processor can also be other general-purpose processors, digital signal processing (Digital Signal Processing, DSP for short), dedicated Integrated circuits (Application Specific Integrated Circuit, ASIC), field-programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems and devices described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be described again here.

It should be understood that the system chip provided by this application can be applied to a variety of terminal equipment and network equipment.

Through the description of the above embodiments, those skilled in the art can understand that for the convenience and simplicity of description, only the division of the above functional modules is used as an example. In practical applications, the above functions can be allocated to different modules according to needs. The functional module is completed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above.

In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods, for example, multiple units or components may be The combination can either be integrated into another device, or some features can be omitted, or not implemented. On the other hand, the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, and the indirect coupling or communication connection of the devices or units may be in electrical, mechanical or other forms.

The units described as separate components may or may not be physically separated. The components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place, or they may be distributed to multiple different places. . Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in each embodiment of the present application can be integrated into one processing unit, each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated units can be implemented in the form of hardware or software functional units.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of the present application are essentially or contribute to the existing technology, or all or part of the technical solution can be embodied in the form of a software product, and the software product is stored in a storage medium , including several instructions to cause a device (which can be a microcontroller, a chip, etc.) or a processor to execute all or part of the steps of the methods described in various embodiments of this application. The aforementioned storage media include: U disk, mobile hard disk, ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

The above contents are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of changes or replacements within the technical scope disclosed in the present application, and should are covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

A transimpedance amplifier with filtering function, characterized in that the transimpedance amplifier has an open-loop structure and includes a differential input terminal and a differential output terminal. The differential input terminal includes a positive input terminal and a negative input terminal. The differential input terminal includes a positive input terminal and a negative input terminal. The output terminal includes a positive output terminal and a negative output terminal;

A first amplification circuit and a first load are coupled to the first signal path where the positive input terminal and the negative output terminal are located, and a third signal path is coupled to the second signal path where the negative input terminal and the positive output terminal are located. two amplification circuits and a second load, a first amplifier coupled between the first amplification circuit and the second amplification circuit;

The first amplifier circuit is used to control the current flowing through the first load;

The second amplifier circuit is used to control the current flowing through the second load;

The first amplifier is used to improve the filtering characteristics of the first signal path and to improve the filtering characteristics of the second signal path.
The transimpedance amplifier according to claim 1, characterized in that:

The first amplification circuit and the first load connected in series are coupled to the first signal path where the positive input terminal and the negative output terminal are located; the first amplification circuit includes a circuit connected across the first switching device. a first capacitor and a second capacitor, and a first current source coupled to the positive input terminal;

The second signal path where the negative input terminal and the positive output terminal are located is coupled with the second amplification circuit and the second load in series; the second amplification circuit includes a second signal path connected across the second switching device. a third capacitor and a fourth capacitor, and a second current source coupled to the negative input terminal.
The transimpedance amplifier according to claim 2, characterized in that:

The first terminal of the first switching device is coupled to the first terminal of the first load, the second terminal of the first switching device is coupled to the positive input terminal, and the first terminal of the first switching device is coupled to the first terminal of the first load. The first capacitor is connected across the second end of the first switching device, and the second capacitor is connected across the second end of the first switching device and the third end of the first switching device, The first output terminal of the first amplifier is coupled between the first terminal of the second capacitor and the third terminal of the first switching device, and the first input terminal of the first amplifier is coupled between the positive terminal and the first terminal of the first switching device. between the input terminal and the first terminal of the first current source;

The first terminal of the second switching device is coupled to the first terminal of the second load, the second terminal of the second switching device is coupled to the negative input terminal, and the first terminal of the second switching device is coupled to the first terminal of the second load. The third capacitor is connected across the second end of the second switching device, the fourth capacitor is connected across the second end of the second switching device and the third end of the second switching device, and The second output terminal of the first amplifier is coupled between the first terminal of the fourth capacitor and the third terminal of the second switching device, and the second input terminal of the first amplifier is coupled to the negative input terminal. and between the first terminal of the second current source;

The second end of the first load is coupled to the second end of the second load;

The second terminal of the first current source is coupled to the second terminal of the second current source.
The transimpedance amplifier according to claim 2 or 3, characterized in that the first current source is used to generate a first quiescent current, and the first quiescent current flows through the first load so that the negative output The gain of the terminal changes with the change of the resistance of the first load;

The second current source is used to generate a second quiescent current, and the second quiescent current flows through the second load, so that the gain of the positive output terminal changes as the resistance of the second load changes.
The transimpedance amplifier according to any one of claims 2-4, characterized in that,

The second capacitor and the first switching device generate a first pole, and the first load and the first capacitor generate a second pole;

The fourth capacitor and the second switching device generate a third pole, and the second load and the third capacitor generate a fourth pole.
The transimpedance amplifier according to claim 5, characterized in that:

When the first capacitor is connected across the first end of the first switching device and the second end of the first switching device, a first zero point of feedforward is generated; the first amplifier is used to control the The position of the first zero point is at a high frequency, so that the first signal path has a second-order filter characteristic;

When the third capacitor is connected across the first end of the second switching device and the second end of the second switching device, a feedforward second zero point is generated; the second amplifier is used to control the The position of the second zero point is at a high frequency, so that the second signal path has a second-order filter characteristic.
The transimpedance amplifier according to claim 1, characterized in that the transimpedance amplifier further includes a voltage stabilizing circuit, the voltage stabilizing circuit is used to form negative feedback and control the voltage of the positive output terminal and the voltage of the positive output terminal. The voltage at the negative output remains consistent with the reference voltage.
The transimpedance amplifier according to claim 7, characterized in that:

The voltage stabilizing circuit includes a third switching device and a fourth switching device coupled in series, and also includes a second amplifier;

The signal path where the third switching device and the fourth switching device are located and the signal path where the first load and the second load are located are coupled in parallel between the positive output terminal and the negative output terminal;

The output terminal of the second amplifier is coupled between the gate electrode of the third switching device and the gate electrode of the fourth switching device; the first input terminal of the second amplifier is coupled between the first input terminal coupled in series. Between the load and the second load, the second input terminal of the second amplifier is used to input the reference voltage.
A radio frequency receiving device, characterized in that the radio frequency receiving device includes a transimpedance amplifier with a filtering function according to any one of claims 1 to 8.
A chip, characterized in that the chip includes the radio frequency receiving device according to claim 9.