Abstract: An active quench circuit for an avalanche current device applies a bias voltage to reverse bias an avalanche current device above its avalanche breakdown voltage; a current amplifier circuit having a turn-off speed slower than the avalanche speed of the avalanche device and responsive to the avalanche current of the avalanche device generates an overshoot current continuing after the end of the avalanche current; and a feedback circuit responsive to the overshoot current generates a quenching voltage for reducing the bias voltage below the avalanche breakdown voltage to quench the avalanche current of the avalanche device.