AGC for Radar, Self-Driving, and Drone Applications

Circuit schematic for an Automatic Gain Control (AGC) used in radar self-driving and drone applications, featuring operational amplifiers, diodes, and resistors to regulate signal amplitude.

This automatic gain control (AGC) circuit features a non-inverting op-amp with a voltage-controlled resistor — a JFET — that adjusts the amplifier’s gain. The output drives a full-wave rectifier, which feeds an integrator acting as a low-pass filter to minimize ripple and distortion.

Using an op-amp diode topology, the circuit produces a full-wave rectified DC signal, controlling the JFET’s drain-to-source resistance. This dynamic resistance adjusts the amplifier’s gain to maintain a consistent 0.2 V peak-to-peak output. Originally designed for radar-based object detection, this AGC approach can be extended to drones, unmanned vehicles, and self-driving cars.

📚 Source: C. Marco, Automatic Gain Control Operates Over Two Decades, Electronics, Aug. 16, 1973; reprinted in Circuits for Electronics Engineers, Electronics, 1977.

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