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 plusmn0.5 V and the load is 15 pF. The opamp attains a DC gain of 100 dB, a unity-gain frequency of 40 MHz, a phase margin of 64deg and a low power consumption of 720 muW. The small-signal behavior variation is only plusmn2.2%. The large-signal behavior is also verified to be constant.
The charge pumping technique is shown to be a very efficient method for studying the slow traps in the oxide of metal–oxide–semiconductor (MOS) transistors. The trap concentration is obtained by varying the gate pulse frequency, the other measurement parameters being kept constant. The concentrations measured on virgin devices are in agreement with those generally obtained on state‐of‐the‐art MOS transistors using noise measurements. On virgin and stressed devices, they also agree with those measured using a drain current transient technique. The concentration profiles show an increase of the trap density near the oxide–semiconductor interface.