A High Speed Rail-to-Rail Operational Amplifier with Constant-gm for LVDS Receiver

A rail-to-rail operational amplifier with constant-gm for LVDS (Low-Voltage Differential Signal) Receiver is presented in this paper. The constant-gm is come true by compensation circuit which is consisted of two parallel-connected complementary differential pairs. The current summing stage is made up of a folded cascade with a current comparator for Gb/s transmission rates. The circuit achieved in SMIC 130nm CMOS technology. Simulation result shows that the gm variation in the entire input range (0~3.3V) is constant within 3.1%, the Op-Amp performs 5.6-dB DC gain, 1.36-GHz bandwidth, and phase margin is 60.9 at 3.3V power supply.