A low voltage CMOS rail-to-rail operational amplifier based on flipped differential pairs

This paper introduces a CMOS operational amplifier with constant transconductance, suitable for operation in low voltage environments. A constant transconductance is ensured for the whole common mode input stage which is based on flipped differential pairs. The proposed operational amplifier is designed to operate with a 1-V supply and is implemented in 0.18-μm standard CMOS technology. The results show that a closed-loop unity-gain bandwidth achieves 7.6 MHz and an open-loop low-frequency gain is higher than 73 dB with a 1-MΩ||15-pF load.