Low-voltage closed-loop amplifier circuits based on quasi-floating gate transistors

A novel design technique for closed-loop amplifier circuits, suited to very low supply voltages, is proposed. It is based on the use of quasi-floating gate MOS transistors, thus avoiding issues encountered in true floating-gate MOS structures such as initial floating gate charge and gain-bandwidth product degradation. A programmable-gain inverting amplifier, a digital to analog converter, and a sample and hold circuit, all based on this technique, are presented along with simulation results, thus illustrating the proposed approach.