Design of low-voltage CMOS amplifier with high electromagnetic interference immunity

Based on CMOS bulk-driven structure, a low-voltage amplifier with high electromagnetic interference (EMI) immunity is proposed. In the circuit, a partial positive feedback enhances its effective transconductance and an input voltage-drop structure modifies its direct current (DC) nonlinearity. For the overall amplifier, a dual input-stage guarantees its good alternating current (AC) feature, and a symmetrical topology ensures its symmetry and symmetrical slew rate (SR). The amplifier was implemented in a 0.35 μm standard CMOS process using 1V power supply. Theoretical analysis and simulation results for EMI robustness are presented and compared with the classical bulk-driven amplifier. The results show that the offset voltage of the proposed amplifier is less than 50 mV and the output power spectrum density (PSD) at 10 kHz is 33 dBm lower than that of the classical structure.