Summing amplifier for developing a squelch and meter voltage in a radio receiver

摘要

In a radio receiver IF amplifier, a high gain AGC circuit produces a constant signal output regardless of input signal levels in excess of a threshold value. A summing amplifier responds to the AGC voltage and the IF amplifier current to develop a d-c potential directly proportional to the signal input to the amplifier both above and below the AGC threshold. This voltage is useful in the squelch and signal strength meter circuits.