Very low voltage operational amplifiers using floating gate MOS transistor

A threshold voltage tunable operational amplifier (op-amp) structure that can be operated with a very low power supply is presented. The use of floating gate MOS transistors as the basic op-amp circuit elements makes it possible to obtain a very low voltage op-amp because of the threshold voltage adjustability of the floating gate transistors. Good matching can also be achieved by tuning the threshold voltages. A two-step threshold voltage tuning scheme is presented. Due to the long term charge retention property of the floating gate transistors, threshold voltage tuning does not have to be done frequently, and near continuous-time operation of the op-amp can be achieved