A wide range and high speed automatic gain control

Automatic gain control (AGC) techniques have been largely used since the beginning of electronics but in most of the applications the dynamic response is slow compared with the carrier frequency. The problem of developing an automatic gain control having simultaneously high dynamic response and wide control range is analyzed in this work. An ideal gain control law, having the property that the total loop gain remains constant independent of the carrier amplitude, is obtained. The resulting AGC behavior is compared, by computer simulations, with a linear multiplier AGC. The ideal gain control law can be approximated by using a transconductance amplifier. A practical circuit that has been used at CERN in the radiofrequency loops of the Booster Synchrotron is presented. The circuit has high speed and 80 dB gain control range.<>