| 摘要 |
A class-AB audio amplifier comprises, as a final stage, two complementary power transistors connected across a direct-current source in series with an output resistor whose junction with the first of these transistors is grounded through a capacitor. The bases of the power transistors are connected across a biasing resistance inserted between two complementary pilot transistors which are connected across the d-c source in series with a constant-current generator, one of these pilot transistors having its base connected to a signal input while the other forms part of a differential circuit also including a feedback transistor of the same conductivity type connected across the source in series with the constant-current generator. With the base of the last-mentioned pilot transistor held at a constant potential through a Zener diode and the base of the feedback transistor tied to the aforementioned junction, any change in the junction potential is compensated by a variation in the current flow through the biasing resistance modifying the conductivity of the first power transistor to keep its current substantially constant, that current flowing alternately into the second power transistor and into a capacitor connected across the latter transistor in series with a load. |
