Design and implementation of an improved constant-Gm bias circuit

Automatic frequency tuning circuit of on-chip Gm-C filter has so many problems such as complex structure, high power consumption and low precision. In order to solve these problems, an improved constant-Gm bias circuit was designed in this paper. The circuit has been analyzed theoretically in detail. Simulation results show that the circuit simplified the structure of frequency tuning circuit, circuit area and power dissipation are reduced, and the deviation is less than 6.5% under different process corners and large temperature variation range. The circuit was applied to the 7th order low pass filter for wireless sensor chips.