High-resolution hold-off time control circuit for geiger-mode avalanche photodiodes

A high-resolution hold-off time control circuit for Geiger-mode avalanche photodiodes (GM-APDs) that enables linear changes to the hold-off time from several nanoseconds to microseconds is presented. The resolution of the hold-off time can be varied from nanoseconds to tens of nanoseconds with a range up to 1.2 μs to cater for a variety of GM-APDs. This circuit allows setting of the optimal `afterpulse-free´ hold-off time for any GM-APD through digital inputs or additional signal processing circuitry. The layout area is 95 μm × 55 μm which makes it suitable for use with APD arrays. The APD is automatically reset following the end of the hold-off period.