Design of an adjustable bias circuit using a single-sided CMOS supply for avalanche photodiodes

A charge pump circuit operating from a single-sided CMOS supply, capable of biasing avalanche photodiodes up to 40 V with load currents in the mA range is presented. This circuit introduces new design elements that overcome previously published limitations. These elements include pass-gate voltage regulators and a mechanism for linking the negative voltage regulator to the positive voltage output. This design allows linear adjustment of the output voltage from a single control voltage. The circuit has compact dimensions of 1.55 mm × 1 mm, including bond pads, which makes it suitable for hybrid integration in a single package with an APD and two surface-mount capacitors.