Low-cost power amplifiers with silicon transistors

Characteristics of silicon and germanium power transistors used in power output stages of audio amplifiers are discussed. The higher junction temperature and lower I
CBO
of silicon are the major advantages. A high-voltage class A audio amplifier with the advantages of a direct-coupled drive circuit is discussed. Low-cost semiconductors are used to replace electrolytic capacitors. The advantages of transformerless push-pull circuits and capacitive vs. direct coupling to the load are also discussed. Both
2\frac{1}{2}
-watt and 20-watt circuits are described and shown to give high performance and to protect the output transistors against overdrive.