A Low-Noise, Wideband, Integrated CMOS Transimpedance Preamplifier for Photodiode Applications

A low-noise, wideband, integrated CMOS transimpedance preamplifier is presented for silicon avalanche photodiode (APD) applications. The preamplifier, fabricated in a standard 2-µ CMOS technology, features a transimpedance gain of 45 kΩ, a risetime of 22 ns, a series noise of 1.6 n V /Hz½ and a wideband equivalent input-noise current of 12 nA for a source capacitance of 12 pF. The measured 22Na timing resolution of 9.2-ns FWHM and energy resolution of 22.4% FWHM for the RCA C30994 BGO/APD detector module coupled to the preamplifier is comparable to the performance reported using charge-sensitive preamplifiers, This illustrates that transimpedance preamplifiers should be considered for APD applications, especially where APD noise current dominates noise from feedback resistors in the 10-kΩ to 50-kΩ range. The transimpedance preamplifier reported here offers advantages of being fully monolithically integrated, having low power dissipation (38 mW), having low bandwidth sensitivity to source capacitance, requiring no shaping-amplifier pole-zero compensation, and requiring no feedback capacitance reset at high count rates.