Electronic – High Frequency Capacitors in Differential Amplifier

amplifiercapacitordifferentialvoltage-amplification

I am curious about the function of two capacitors near differential transistor pair amplifier. The circuit picture is cut out of one of Pioneer's audio amplifiers. This amplifier is basically complementary differential pair that drives VAS and Emitter Follower.

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I am interested in the functions of capacitor C133 (47 pF) and C141 (470 pF) – what is their purpose in such circuit? The function of C132 is the dominant pole compensation, which I understand, but the other two (red squares) seems to me like another high frequency bypass capacitor, according to their values.

Best Answer

Or this way

schematic

simulate this circuit – Schematic created using CircuitLab

Where the input stage (IPS) is a transconductance amplifier converting the voltage difference between two input into a current (Iout/Vin = gm).

The secend stage is VAS is a transimpedance amplifier that takes its input current from the first stage and outputs a voltage (Vout/Iin = Z)

The third stage, the power gain stage, has a voltage gain 1.

And I fix the original diagram.

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