| 摘要 |
Audio inputs to be amplified pass to an input stage, and then to a double differential transistor stage (4), the inverting input of which is used for the overall negative feedback. The double differential amplifier is fed by symmetrical constant current sources (5,6) from the positive and negative rails, at a bias current causing them to run at a temp. above ambient, such as 50 or 60 deg. C. The point of reference of the transistor stage floats with respect to earth because of a resistor across the rails (9).The stage (A) made up of the double differential amplifier and constant current source treats positive and negative components of an AC signal equally, before passing the signals to a level shifting stage (B) via two symmetrical transistors (16,17). The final stage is a push-pull power amplifier (C) which drives a loudspeaker.
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