Transistor voice control amplifier circuit

It is a two-stage directly coupled transistor amplifier. The collector voltage U<i of the first-stage amplifier tube VT1 is
the ratio of the base voltage U of the second-stage amplifier VI and 2. The stability of the DC operating point is
proportional to the current passing through VT2 1 RF. UF is added to the base of VT1 after dividing the voltage by wind and RF.
The voltage amplification factor of this circuit is equal to the product of the two-stage amplification factors. The stable feedback process of circuit operation
is as follows: when the emitter current of VT2 increases, UF rises
, and is divided by R1 and R, causing Ultl to rise. Vn thus reduces the conduction degree of VT2
, the current flowing through the emitter resistor RF is reduced, and the circuit returns to normal operation, achieving
the purpose of stable operation.
    The transistor directly coupled voltage negative feedback dog circuit not only has high voltage
Pressure magnification, and stable working performance.
    In the circuit, the emitter resistance Rf of VT1. No bypass capacitor is added, indicating that it not
only has DC negative feedback, but also AC negative feedback. Although this kind of negative feedback circuit
loses part of the amplification factor, what it gains is the stability of the circuit operation.
The emitter resistance of VT2 is divided into two parts, and Re2 is added with a bypass capacitor G, so that it only
has DC negative feedback but no AC negative feedback.