Upper and lower symmetrical negative feedback mode field effect transistor power amplifier 02

The power amplifier adopts an upper and lower symmetrical negative feedback method. The output terminals R7 and R8 are fed back up and down to the emitters
of the front stage VT1 and VT2 respectively . The upper negative feedback circuit is composed of R7, R5 and ci; while R6, R8 and C2 Form the lower negative feedback circuit. The upper and lower feedback are independent and do not interfere with each other. 6 This feedback method is completely different from the common upper and lower symmetrical differential amplifier circuits . The power supply pulsation noise of common differential amplifiers can easily mix into the emitter of the front-stage transistor , resulting in a poor signal-to-noise ratio of the circuit. . However, this machine has overcome this shortcoming. R3 and R4 form a pulse filter with cl and C2 respectively, which prevents the pulsating noise of the power supply from entering the emitter of the front stage and further improves the signal-to-noise ratio of this machine. This is the characteristic of this machine. Special feature. In addition, RS.R6 also plays a role in controlling the current negative feedback of the front stage to prevent the gain of the upper and lower symmetrical circuits from being too large, and also plays a self-adjusting function to suppress the nFE deviation of the transistor 6, which cannot be achieved by common differential amplifier circuits.