A power amplifier with an automatic bias control circuit is disclosed. The amplifier includes two complementary Darlington pairs operating in a push-pull mode providing output power. A bias control network including a switching transistor is coupled to the base circuits of the Darlington pairs for controlling...http://www.google.de/patents/US4077013?utm_source=gb-gplus-sharePatent US4077013 - Audio power amplifier with automatic bias control
