Very Low Voltage Rail-to-Rail Programmable-Gain CMOS Amplifier

A novel design technique for operating closed-loop amplifier circuits at very low supply voltages is proposed. It is based on the use of quasi-floating gate transistors, avoiding issues encountered in true floating-gate structures such as the initial floating-gate charge, offset drift with temperature, and the gain-bandwidth product degradation. A programmable-gain differential amplifier is designed and implemented following this method. Measurement results of an experimental prototype fabricated in a 0.5-μm CMOS technology validate on silicon the proposed technique.