Patent ID: 8521114

Claim:
An Automatic Gain Control (AGC) circuit comprising: a PIN-diode attenuator having an attenuator input and an attenuator output; a control circuit connected to the attenuator so as to read a signal at the attenuator output, the control circuit being configured to supply a feedback control signal to the attenuator based on an error signal between the signal read at the attenuator output and a reference signal, so as to modulate an attenuation level of the attenuator and maintain a substantially constant power level at the attenuator output, the control circuit comprising at least a resistor and a capacitor which define a time constant of the AGC circuit, the AGC circuit featuring a main pole depending on the time constant and on a voltage of the feedback control signal, wherein the control circuit further comprises: an integrator stage including an integrator operational amplifier configured to integrate the error signal responsive to the signal at the attenuator output and the first reference signal, and provide the feedback control signal at an integrator output; and a variable gain block coupled to the integrator output and including a gain element formed with a gain operational amplifier and a gain variation element formed with a junction field-effect transistor (JFET) coupled to an input of the gain operational amplifier, the variable gain block configured to receive the feedback control signal and modulate the main pole proportionally to a variable gain of the variable gain block, the variable gain being varied substantially inversely to the voltage of the feedback control signal and the JFET configured to perform gain control of the variable gain in accordance with a voltage applied to a gate terminal thereof.