In modern clinical applications, Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) waves are normally recorded by massive and powerhungry instruments. In order to enhance the portability of biopotential signal measurements, in this paper, we describe the design and implementation of a low-power and low-noise biopotential signal readout front-end (RFE). Designed in 90-nm CMOS with thick-oxide transistors, the RFE consists of an instrumentation amplifier (IA) with both chopper and ACcoupling techniques for: dc-offset removals; filtering the transistors' flicker noise and boosting the CMRR. Following the IA there is a spike filter, which is clocked accurately to suppress the chopping spikes. The final stage is a gain-bandwidthcontrollable amplifier, which further boosts the gain and enables different bio-potential signal measurements through simple digital controls. Simulation results showed that the RFE can successfully eliminate the differential electrode offset up to ±50 mV, while achieving 140-dB CMRR and 60.2-nV/√Hz input-referred noise spectral density. The entire RFE consumes 16.55 µA from a single 3-V supply.