| 摘要 |
The transistor television intermediate frequency amplifier has variable gain controlled by automatic gain control current feedback. A transistor is biased in a common emitter mode with signals fed into the base junction and output taken from the collector. The collector has a variable impedance load formed by the base and emitter of a second transistor. Feedback current fed into the emitter of the second transistor flows to ground through the collector but alters the base emitter impedance and hence the gain of the amplifier. Two amplifiers with a common feedback current may be connected as a variable gain differential amplifier.
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