Rail-to-rail operational amplifier with stabilized frequency response and constant-gm input stage

In this paper a 3 V input and output Rail-to-Rail operational amplifer is designed in a 0.6 pm CMOS technology. It uses a complementary differential input stage, a simple class-A output stage and two current compensation networks. The first provides constant transconductance at the input by varying the square root of the input pairs' tail currents. The second ensures an almost constant frequency response throughout the entire common mode range of operation. Simulations show a maximum variation of only 9 % and 30 % for PM and GM respectively. Large-signal step response achieves a 0.1 % settling time lower than 32 ns, while its quiescent power consumption is 3.7mW.