Patent ID: 7939790

Claim:
A method for biasing an APD, comprising: developing a first output signal s(v 1 ) from the APD when biased with a first bias voltage v 1 and developing a second output signal s(v 2 ) from the APD when biased with a second bias voltage v 2 , wherein s(v)=PRZM(v), (P) is an light power illuminating the APD, R is a responsivity of the APD, M(v) is an APD avalanche gain and Z is a trans-impedance amplifier gain (Z); acquiring a ratio r=s(v 1 )/s(v 2 )=PRZM(v 1 )/[PRZM(v 2 )]=M(v 1 )/M(v 2 ); and invoking a feedback control method to bias the APD using the ratio r.