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 ICBOof 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 -watt and 20-watt circuits are described and shown to give high performance and to protect the output transistors against overdrive.