Protective circuit for two-stage pushpull chopper - has complementary transistors in first stage with emitters positively and negatively based

摘要

The protective circuit for a two-stage push-pull chopper has complementary transistors in the first stage. The emitters are biased with a positive and a negative voltage. Transistors of the same type in the second stage are connected by collectors to the supply voltage's positive and negative terminals. Emitter-collector path of a protective transistor (T1, T2) is in parallel with the base-emitter path of chopper transistors (T3,T4). A capacitor (C1,C2) and a resistor (R3,R4) are in parallel with transistors (T1,T2). Diodes (D3,D5;D4,D6) are between bases of chopper transistors (T3,T4) and collectors of transistors (T1,T2). A further resistor (R1,R2) connects transistor (T1,T2) collectors to the diodes.