| 摘要 |
The automatic gain control (a.g.c) circuit comprises a basic a.g.c. transistor amplifier whose emitter-collector conductance is varied by a control voltage, which is derived from the envelope of the amplifier output voltage which is well known. The invention involves the use of a digital-toanalog converter that is controlled by a digital-updown counter. The counter is controlled by a window comparator that compares the rectified output voltage of the amplifier with a reference voltage level and its upper and lower limits. If the output voltage exceeds either limit, the counter is enabled and the appropriate up or down indication is given.
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