A 1-V 5 /spl mu/W CMOS-opamp with bulk-driven input transistors

In this paper, a low-power CMOS operational amplifier for biomedical instrumentation operating with a 1-V supply is described. Large input common-mode range (CMR) is achieved utilizing bulk-driven PMOS-transistors as an input differential pair of the opamp. The opamp was fabricated in a 0.35 /spl mu/m n-well double-poly CMOS process with threshold voltages of 0.5 V and 0.65 V. The open-loop gain (A/sub 0/) of the amplifier is 70 dB, the gain-bandwidth product (GBW) is 190 kHz and the phase margin (PM) is 60/spl deg/ with a 7 pF load. The power consumption of the opamp is 5 /spl mu/W.