Information of extracted biopotential signals such as ECG, EEG and EMG is widely used for medical treatment purpose and health care applications. There is an increasing demand for flexible/portable biopotential signal acquisition systems which can be not only applied for long time medical monitoring, but also extended to home health care, sports and entertainment applications. The key to this kind of systems is the analog readout front-end. The analog readout front-end extracts the biosignals directly from human body and defines the extracted signal quality. The most critical and power consuming building block of the readout front-end circuit is the biopotential amplifier. Biopotential amplifier emerges several design challenges due to the complex environment of human body and different applications. In general, biopotential amplifier should have high CMRR to reject strong common mode interference from mains and low noise in order to acquire the extremely weak signals. This thesis proposes a novel flexible analog readout front-end circuit topology oriented to flexible and portable biopotential signal acquisition systems. The essential contribution of this work is the new chopped current mode instrumentation amplifier (CMIA) based on second generation current conveyor while involving power supply current sensing technique. The new CMIA gains very low noise performance by using chopper modulation technique. At the same time, high CMRR, low power consumption and other advantages are achieved by the aid of the current mode topology and current sensing technique realized by the new designed low transconductance current mirrors. Two complete analog readout front-ends are implemented and simulated using the proposed chopped CMIA with two advanced low pass filters (LPFs): general purpose readout front-end using 100-Hz 5th-order Gm-C LPF and portable EEG readout frontend using 40-Hz source-follower-based LPF. The simulation results show that the designed circuits meet the basic requirements of the long time portable biopotential acquisition application and are ready for connecting to next stages, e.g. ADC and DSP.