A comparative overview of two transimpedance amplifiers for biosensing applications

This work compares two CMOS front-end transimpedance amplifiers (TIA) for use in optical biosensors. They are the shunt-feedback and current-mode circuits, the most widely used for wideband operation. The former consists of a three-stage nested-Miller-compensated (NMC) amplifier in non-inverting mode with a photodiode (PD) bootstrapping and a controlled voltage gain; the latter comprises a wideband common-gate feedback (CGFB) current mirror coupled to a current-to-voltage conversion stage and two common-source gain stages. The simulation results show that the shunt-feedback TIA achieves a maximal gain of 112 dBΩ over a 2 MHz bandwidth, whereas the current-mode TIA has a flat gain of roughly 83 dBΩ over a 115 MHz bandwidth. The overall input rms noise of each circuit was 185pA/√Hz and 53nA/√Hz, respectively, with power consumptions of 0.5 mW and 28.6 mW. It is concluded that the shunt-feedback TIA is a better choice for low to mid-frequency applications.