Symmetrical Push-Pull Operation

Author: Leonard Krugman

Fig. 5-22. A symmetrical push-pull stage.

Figure 5-22 illustrates the basic symmetrical push-pull circuit with numerical values based on the same typical transistor characteristics used in previous examples. The operation of this circuit is the same as that of the transistor push-pull Class A amplifier that uses only one type of transistor. The circuit is capable of supplying a high voltage gain when operating into a high impedance load. The voltage gain of the circuit shown in Fig. 5-22 is in the order of 250 (48db). If the transistors are exactly symmetrical, the d-c collector currents supplied by each transistor cancel each other, and no d-c component flows in the load. The circuit is easily adaptable for direct connection to the voice coil of a speaker. Notice also that the same circuit can be modified by proper adjustment of the base bias for Class B push-pull operation.