edwin amplifier

The Edwin amplifier is unusual in that it embodies two types of output stage in one amplifier. A class A output stage handles the low level signals and also serves as a driver for a class B stage which handles the larger outputs. The principle of operation is shown in figure I. T2 and T3 are biased on by the voltage drop across the diodes D1-D3. T2 and T3 function as a class A stage at low signal levels supplying current to the load via resistors R. As the signal is in creased the voltage drop across these resistors becomes sufficient to cause T4 and TS to conduct and the class B part of the output stage begins to operate. Crossover distortion is quite low with this type of design.