Low voltage, high speed fully differential CMOS op amp

This paper presents a high speed Class AB fully differential op amp capable of operation at supply voltages down to 1.4 V. A standard 0.8 μm CMOS process with a V_T of 0.75 V has been used in this design. A novel cascode input stage has been designed which allows control of its output common mode circuitry and thus accurate control of the output stage quiescent current can be achieved, without additional common mode feedback networks, except for the one which is required for the output stage. The proposed op amp achieves a GBW of 35 MHz and a slew rate of 210 V/μs when operated at 1.8 V and should be useful for most switched capacitor circuits operating at a clock frequency of 13 MHz