An photodetector circuit comprising an avalanche photodiode having a signal input for receiving an input optical signal to be converted to an electrical signal. The photodetector circuit further includes biasing circuitry, coupled to the avalanche photodiode, for applying a bias voltage to the avalanche diode. The bias circuitry includes: (1) a dc bias circuit for providing a dc component to the bias voltage for maintaining the avalanche diode in a stable avalanche gain condition when receiving the input optical signal; and (2) a modulating circuit for providing a high frequency modulating component to the bias voltage for modulating the bias voltage in a manner that enhances the operational characteristics of the avalanche photodiode. In particular, the modulating component to the bias voltage decrease the noise of the signal output of the avalanche photodiode for a given average gain, and increases the bandwidth of the signal output of the avalanche photodiode for a given average gain.