High-gain differential CMOS transimpedance amplifier with on-chip buried double junction photodiode

Introduction: The transimpedance amplifier (TIA) is widely used in optical receiver circuits. The majority of CMOS TIA designs reported in the literature are intended for high speed digital signal reception. The TIA reported in this Letter is optimised for low noise analogue optical signal detection, in a situation where a weak modulated optical signal is superimposed on a large DC background. This type of signal may be encountered for example in optical coherence tomography (OCT) [1]. Specifically, our design is optimised to detect a 100 kHz carrier frequency, 5 kHz bandwidth signal, and to reject an unwanted DC component with 50 dB attenuation compared to the signal band gain. Our TIA differs from other similar designs [2, 3] through the unique combination of an on-chip buried double junction (BDJ) photodiode, very high adjustable gain and attendant low noise.