I. Introduction
TIA specifications for systems requiring monolithically integrated arrays, like optical interconnects [1] are somewhat different from that for single channel receivers. For integrating multiple channels on a tight inter-channel pitch, low power and low circuit area usage are desirable. Power constraints usually lead to inductive BW extension techniques in TIA design [2] [3]. However, these approaches are not feasible for arrays owing to their large area cost. [4] is a notable exception wherein excellent power to BW ratio was achieved using reasonably sized inductors in 80 nm CMOS technology, but the high noise floor limits that work to short-haul links. Negative capacitance has been used in the past to reduce the effective capacitance looking into the gate/base of the active device [5] [6]; this work exploits that idea as a means of BW extension for shunt feedback TIA's in the presence of significant extrinsic input capacitance. Shunt feedback TIA's are conveniently represented by the simplified model of Fig. 1 which consists of a voltage amplifier-A around which a shunt feedback is applied with . Using the simplest topology (e.g. common emitter) for the voltage amplifier has many advantages a) low noise due to fewer components b) lower supply voltage c) compact area. The main drawback is the large capacitance seen at the input node of the TIA due to the photodetector , ESD protection diodes , bondpad and the input capacitance of the amplifying transistor . This total capacitance coupled with the relatively high input impedance given by , poses a fundamental BW bottleneck which is difficult to eliminate without compromise. Furthermore, from the expression it is clear that input impedance and transimpedance gain are coupled, making the realization of high-gain high-BW TIA's difficult. Previously reported solutions include - use of multi-stage topologies [7], regulated cascode [8], and negative impedance compensation [9]. These techniques require additional area and power, and also degrade noise performance significantly. General representation of Shunt Feedback TIA's