SU1259472A1 - Operational amplifier - Google Patents

Abstract

The invention relates to radio engineering and extends the frequency band while reducing the power consumption. The device contains an input differential stage 1, performed on transistors 2, 3 with a current generator 4, an intermediate stage 5, performed on transistors (T) 6-9 of a current-generating element 10, an offset circuit 11, a current reflector 12, an output push-pull stage 13, T 14, capacitor 15. The use of reflector 12 to bias T 6 - 9 provides equal emitter currents T 6, 7. This determines the symmetrical load of stage 1, providing a high common-mode rejection ratio. This is facilitated by the absence of asymmetric gain in the device stages. The output impedance of the reflector 12 exceeds the output impedance T 9 and practically does not shunt it. In this case, the amplifying properties of the cascade 5 are used, which provides a large amplitude of the output signal. In any mode, the amplifier is corrected by a single capacitor 15, which allows for a smooth frequency response. 1 il. (L o w ate si n9

Description

The invention relates to radio engineering and can be used to amplify and convert signals with high accuracy over a wide frequency band.

The purpose of the invention is to expand the frequency band while reducing power consumption.

The drawing shows a circuit diagram of an operating system.

The operational amplifier contains an input differential stage 1, performed on transistors 2 and 3c by a current generator 4, an intermediate stage 5 performed on the first second, third and fourth transistors 6 9, current supply element 10, bias circuit 11 (output two-stroke stage), current reflector 12 , output push-pull stage 13, additional transistor 14, capacitor 15,

The operational amplifier operates as follows.

When power is supplied through the current supply element 10, which can be used as a resistor or a field-effect transistor with a p-h junction, current begins to flow. This current is bias for current reflector 12, the output current is equal to the current flowing through the current element giving element 10, and the two branches of intermediate stage 5 are provided with equal bias currents. In addition, since the base of the additional resistor 14 is connected to the input of the current driver 12, a bias current appears symmetrically distributed between the transistors 2 and 3 of the input DC1 in the input differential stage (DC) 1. The voltage drop across the bias circuit 11 provides the necessary initial mode for the transistors of the output push-pull stage 13. Thus, all the transistors of the operational amplifier are in active mode.

The high power gain in the intermediate stage 5 makes it possible to select the bias current of the input DC 1 substantially lower than the bias current of the intermediate stage 5, without worsening the rate of rise of the output voltage of the operational amplifier. In this case, it is always possible to provide such a relationship between

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the resistances of the collector loads of transistors 2 and 3, the bias current of the input DC 1 and the bias current of the intermediate stage 5, at which the power transfer ratio between these stages is close to maximum, and the voltage drop on the collector loads of transistors 2 and 3 does not exceed in rest mode Oh, 1-0, ZV. This small voltage drop allows for a wide input common-mode range and greatly weakens the Miller effect in input DC 1.

Using a current reflector 12 to bias the first, second, third, and fourth transistors 6-9 allows equal emitter currents of the first and second transistors 6 and 7 to be provided, which determines the symmetrical load of the input DC 1, thereby providing a high common-mode suppression ratio . This is facilitated by the absence of asymmetrical amplification in the cascades of an operational amplifier.

The input resistance of the current reflector 12 substantially exceeds the output resistance of the fourth transistor 9 and practically does not shunt it. In this case, the amplifying properties of the intermediate stage 5 are fully used, the circuit of which allows to provide a large amplitude of the output signal.

Despite the low value of the output resistance of the intermediate stage 5, the amplifier in any mode is corrected by a single capacitor 15, allowing it to provide a smooth frequency response of the corrected operational amplifier.

FORUMUA AND 3 ABOUT AND

An operational amplifier containing a series-connected input differential stage with a symmetrical input: and two outputs with a current generator in the bias circuit, an intermediate stage with a symmetrical input, performed on the first and second transistors, whose collectors are combined, and the bases are the corresponding inputs of the intermediate stage, and the third and fourth transistors, have a different type of conductivity, the bases of which are combined and connected to

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the first output of the current-generating elementary transistor, the base of the Katbta, the collector of the fourth transistor is connected to the input of the reflector of the resistor connected to the input of the output current and the second output of the current-output two-stroke cascade and the output of the output element, and the collector A current that differs from the 5th transistor is connected to its base, so that, in order to expand, the emitters of the third and fourth frequency bands are connected to the emitters of the co2 simultaneously. The power consumption between the first and second transistors of the first and fourth resistors, whose collectors of the transistors are inserted into a capacitor, with a corresponding source, is equipped with a current generator at the power supply terminal.

Claims (1)

Claim An operational amplifier containing a series-connected input differential stage with a symmetric input and two outputs with a current generator in the bias circuit, an intermediate stage with a symmetric input, made on the first and second transistors, the collectors of which are combined, and the bases are the corresponding inputs of the intermediate stage, and the third and fourth transistors having a different type of conductivity, the bases of which are combined and connected to the first output of the current-setting element, and the collector of the fourth trans the stator is connected to the input of the output push-pull stage and to the output of the current reflector, characterized in that, in order to expand the frequency band while reducing the power consumption, a capacitor is introduced between the collectors of the first and fourth transistors, while the current generator is made on an additional transistor, base which is connected to the input of the current reflector with the second output of the current-setting element, the collector of the third 5th transistor connected to its base, the emitters of the third and fourth transistors connected to emitters co. Responsibly the first and second transistors, the collectors of which are connected to the corresponding bus of the power source.