a class - g amplifier comprises first , second and third terminals connected to a load , first supply voltage and second supply voltage , respectively , where v 2 & gt ; v 1 . first and second transistors are series - connected between the first and third terminals with the collector of t 1 coupled via first diode to the second terminal . a third emitter follower transistor has a b / e junction coupled between a signal input terminal and base of t 1 . a first current source couples the third terminal and third transistor . a driver circuit includes a first current path between the third terminal and emitter of t 3 comprising , in series , a second current source , a fourth transistor and second diode . a second current path between a junction point and common point comprises , in series , third and fourth diodes and a third current source . base of fourth transistor is connected to junction and its collector is connected to third current source via fifth diode . a low input voltage cuts off second transistior so first transistor connected to second terminal . above a given voltage , driver circuit turns second transistor on so first transistor connected to third terminal . the output thereby attains a voltage equal to second supply voltage minus one b / e voltage .