0.9-V Rail-to-Rail Operational Amplifiers with Adaptive Threshold Voltage Control

Rail-to-rail operational amplifiers with an adaptive threshold voltage control circuit are designed at low supply voltage of 0.9-V. The control circuit using a bulk bias effect acts to keep enough drain-source voltage for the current source transistor connected with sources of the input transistors. Two types of operational amplifier based on the adaptive threshold voltage control technique are developed for 0.9-V supply voltage, and fabricated in a 0.35-mum CMOS process. Experimental results show that the developed control circuits improve input common-mode voltage range