1-V Low-Power Programmable Rail-to-Rail Operational Amplifier With Improved Transconductance Feedback Technique

A low-power process-independent programmable transconductance rail-to-rail operational amplifier (OpAmp) is proposed. It employs an improved transconductance feedback loop that senses the transconductance (g
_mT
) accurately and enforces it to be equal to the conductance of a reference resistor. Experimental results in a 0.13- μm standard CMOS technology under a 1-V power supply demonstrate a continuous programmable g
_mT
range from 87 to 165 μA/V with minimum fluctuation of ±2.4% and programmable deviation less than 4.5% from the reference value. The OpAmp achieves a unity-gain bandwidth of 3.7 MHz with a 95-pF load while only consuming 187 μA of quiescent current. The figure of merit of the proposed OpAmp is 1879 MHz·pF/mA.