Discrete components high input impedance preamplifier

The main circuit is composed of Trl~Tr. It is a three-level direct coupling circuit
, eliminating the need for decoupling capacitors. In the bias current circuit, in order to enable Tr3 to
work at tOOJ1A, a resistor 4z is added to the source. Due to the influence of the deviation of the FET
, the resistor must be adjusted so that the emitter voltage of Tr3 is 5-5.
The bias current of Mo V, Tr2 and Yu rG is 1mA.
    The gain of the circuit depends on the "1+ (chu./a) port, which is about 10 times
(20dB). R4 can be changed according to the purpose. If Ri is reduced to reduce the gain
, the load of the emitter output device Trs will be reduced. is small, so the output signal curve
will also decrease.