HFAN-03.1.1: Digitally Programmable Low-Noise Avalanche Photo Detector (APD) Bias Circuit

Abstract: A circuit is described to bias an avalanche photodiode as used in fiber-optic receivers. The simple boost converter with voltage-doubler output provides a digitally programmed output voltage of 25V to 71V from a 5V supply. Ceramic filter capacitors and intentionally slowed MOSFET switching transitions provide a low noise output.