Field effect transistor OCL power amplifier circuit

It is a fully symmetrical OCL power amplifier circuit composed of field effect transistors .     VTi ~ VT4 form a fully symmetrical dual differential input stage, which has a very high common mode rejection ratio o     VTs. VT6 forms a FET active load type push-pull voltage amplification stage, which has a high voltage amplification factor.     VT7 and VT8 form a complementary push-pull power amplifier output, and the 1000 resistor connected to their gate is the gate current limiting resistor. The 1-Sfl resistor connected to the source is mainly used to test the quiescent current during debugging. Although the negative feedback generated on it has a protective effect similar to that of the emitter resistor of a transistor, for MOS power amplifier tubes, because its drain current itself has a negative temperature coefficient, it is useless without a source resistor. How big a deal.     This amplifier does not use resistors in the AC negative feedback circuit, but uses a capacitor AC negative feedback circuit. Doing this can improve the sound quality. The amplifier gain is determined by the voltage division ratio of the 1200pF and O,OliuF capacitors, which is about 9-3 times. If the o-ol center is changed to O,1plF, the gain is close to 100 times.     Adjusting RPz can adjust the output midpoint voltage, and adjusting 剉)3 can adjust the quiescent current of the output tube. The quiescent current of this machine is 10mAo.