A dual-mode, low-power and low-noise 0.18µm CMOS front-end for optical biosensors

A dual-mode, low-power and low-noise front-end transimpedance amplifier (TIA), intended for use in optical biosensors, is presented. It consists of a three-stage nested-Miller-compensated (NMC) amplifier in a non-inverting mode with a photodiode (PD) bootstrapping and a controlled voltage gain (CVG). The PD front-end can handle properly waveforms with soft and sharp edge transitions. In the former case, it reduces the voltage gain at DC while preserving a high gain in the frequency range of interest; in the latter, it provides a constant voltage gain over the whole TIA bandwidth. The simulation results show that a maximal gain of about 112 dBΩ can be achieved over a 2 MHz bandwidth. The empirical results obtained with a prototype mounted on PCB for blood glucose monitoring are closely correlated with those obtained using a commercial glucose/lactate analyzer.