Photo detecting circuit and noise elimination method

摘要

In a photo detecting circuit using an avalanche photodiode (APD), a pulse noise mask signal indicating the timing of occurrence of a pulse noise is generated by XORing a reverse-bias-pulse application timing signal and its delayed signal. Pulse noises are eliminated by ANDing an output signal of the APD and the pulse noise mask signal. Alternatively, a pulse noise is estimated by taking the average for the output current signal a given number of times. Pulse noises are eliminated by subtracting the estimated pulse noise from the APD output signal (Fig. 1).