A low-voltage low-power fully differential rail-to-rail input/output opamp in 65-nm CMOS

A new fully differential rail-to-rail input/output opamp with constant small- and large-signal behavior fabricated in 65-nm digital CMOS technology is proposed. A novel current-mode common-mode feedback circuit is introduced to regulate the signal behavior. Measurements are done when the supply voltage is ±0.5V and the load is 15pF. The opamp attains a DC gain of 100dB, a unity-gain frequency of 40MHz, a phase margin of 64° and a low power consumption of 720μW. The small-signal behavior variation is only ±2.2%. The large-signal behavior is also verified to be constant.