JPS5852726Y2 - RC Isohatsu Shinki - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an RC phase shift oscillator that improves distortion of the oscillation output waveform at extremely low frequencies.

For example, when a musical tone signal in an electronic musical instrument is amplitude-modulated or frequency-modulated to obtain a so-called tremolo effect or vibrato effect, a sinusoidal extremely low frequency signal of around 1 OHZ or less is required as the modulation signal.

In order to obtain this extremely low frequency signal, conventionally, an RC phase-shifted oscillator is generally used, which is made by positively feeding back the collector output of a transistor to the base of the transistor via a phase-shifting circuit consisting of multiple capacitors and multiple resistors. However, in order to operate this RC phase shift oscillator at an extremely low frequency, it is necessary to increase the feedback signal amount, that is, the output of the transistor.

However, when this transistor is operated with a large amplitude, the transistor becomes saturated and the output waveform is clipped, making it difficult to obtain an extremely low frequency signal close to a sine wave of several Hz.

An object of the present invention is to provide an RC phase shift oscillator that solves the above-mentioned conventional drawbacks by simply adding a simple circuit.

An embodiment of the present invention will be described below with reference to the drawings.

Tr is a transistor whose collector is the output terminal O
Connected to UT and connected to power #4 via load resistor R1.
)-)■, and the □ vine is grounded through a parallel circuit of resistor R2 and capacitor C1.

A is a phase shift circuit connected between the collector and base of the transistor Tr, which includes a capacitor C2 and a resistor R3, a capacitor C3 and a resistor R4, and a capacitor C4 and a resistor R5.
It is composed of a three-stage differentiator circuit.

R6 is a resistor connected between the voltage -1-)V and the base of the transistor Tr, B is a correction circuit, and a diode D is connected in the forward direction between the base of the transistor Tr and the base of the transistor Tr. It is constituted by a series circuit with resistor R7.

Next, the operation of the above configuration will be explained.

The collector output of the transistor Tr is set to 1 by the phase shift circuit A.
This circuit operates in oscillation by being phase-shifted by 80 degrees and positive feedback to the base.

By the way, if this oscillation operation is performed at an extremely low frequency of several Hz, and the transistor Tr is supplying a large amplitude signal from its collector to the phase shift circuit A, then the phase shift circuit A supplies the signal of the transistor Tr. The signal supplied to the base is large, and its positive peak value causes the transistor Tr to
The collector current of transistor Tr tends to become saturated, and the collector output waveform of transistor Tr becomes clipped as shown by the broken line in FIG.

However, by inserting the correction circuit B of the present invention, when the base current of the transistor Tr increases and its collector current approaches saturation, a current also flows into the correction circuit H, suppressing the manual input to the base of the transistor Tr. The collector output waveform of the transistor Tr becomes close to a sine waveform, although some distortion remains, as shown by the solid line in FIG.

The resistor R7 in the series circuit B raises the potential of the cathode of the diode D from the emitter of the transistor Tr by the voltage generated across the resistor R7 due to the current flowing through the series circuit B.

As detailed above, the RC phase-shifting oscillator of the present invention can easily correct the distortion of the oscillation waveform applied to extremely low frequencies by simply adding one diode and one resistor to the conventional RC phase-shifting oscillator. be able to.

Although the phase shift circuit in this embodiment is constructed from a differentiating circuit, it may also be constructed from a conventionally known integrating circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining an embodiment of the present invention, and FIG. 2 is a graph for explaining its operating characteristics. . In the figure, Tr is a transistor, A is a phase shift circuit, B is a correction circuit, R1 to R7 are resistors, C1 to C4 are capacitors, and D is a diode.

Claims (1)

[Scope of utility model registration request] In an extremely low frequency RC phase shift oscillator in which the collector output of a transistor is positively fed back to the base of the transistor via a phase shift circuit consisting of a plurality of capacitors and a plurality of resistors, the saturation distortion of the transistor is removed. In order to
Phase-shifted oscillator.