Discrete components OCL power amplifier circuit

Shown is an OCL power amplifier circuit composed of discrete components . , rri and VT2 form a differential input stage circuit, VT3 tube forms a push stage, VT5 and VT6 are complementary symmetrical output stages, VD4 is the static bias diode of VT5 and VT6 , +Ucc and -Ucc are positive and negative symmetrical power supplies. The working principle of this circuit is almost the same     as that of the circuit shown in Figure 10-12 . The difference is that +Uc, - Ucc symmetrical power supply is used and the output coupling capacitor is omitted.     In the circuit shown in Figure I0-15. VT1, V12 and VT3 are in Category A status, VT5 and VT6 are in Category A and B status. Since VT5 and VT6 have consistent performance and the same static bias, the internal resistance between the collector and emitter of VT5 and VT6 is equal, plus +Ucc and - Ucc are symmetrical, so that the output voltage is 0 V in static state, and the speaker SP1 can be connected directly between the output terminal and ground, and no DC current flows through SP1. The positive half-cycle signal causes VT5 to conduct and amplify, the negative half-cycle signal causes VT6 to conduct and amplify, and a full-wave signal is obtained on SP1.