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9-6: Typical Receiver Circuits
Automatic Gain Control Circuits: Controlling Circuit Gain
The gain of a bipolar transistor amplifier is proportional to the amount of collector current flowing.
Two methods of applying AGC are as follows:
The gain can be decreased by decreasing the collector current. This is called reverse AGC.
The gain can be reduced by increasing the collector current. A stronger signal increases AGC voltage and base current and, in turn, increases collector current, reducing the gain. This method of gain control is known as forward AGC.