This paper describes a 90nm CMOS low-noise low-power biopotential signal readout front-end (RFE). The front-stage instrumentation amplifier (IA) features a chopper; an AC-coupler and a novel chopper notch filter for minimizing the dc-offset; transistors' flicker noise and 50Hz powerline interference concurrently. A noise-aware transistor selection (thin- and thick-oxide) in the IA enables a flexible tradeoff between noise and input impedance performances. The 2 stage is a spike filter clocked by a parallel use of two non-overlapping clock generators, effectively tracking and suppressing the chopper spikes. The last stage is a gain-bandwidth-controllable amplifier for boosting the gain and alleviating different bio-potential signal measurements through simple digital controls. Simulation results showed that the RFE is capable of tolerating a differential electrode offset up to ±50mV, while achieving 140dB CMRR and 51.4nV/√Hz input-referred noise density. The notch at 50Hz achieves 41dB rejection. The entire RFE consumes 16.55 to 35.5μA at 3V.