Abstract
A tunable gm-C filter with cutoff frequency insensitive to Process, Voltage and Temperature is proposed. An external clock frequency is used to generate a current using a switched capacitor circuit. The proposed filter is ideally suited for applications where a tight control on cutoff frequency is desired across different operating conditions of the chip. The circuit was designed in 3.3V BiCMOS technology and simulations were carried out using SPICE. The simulation results show that the total variation in the cutoff frequency is 1% as compared to the 27% variation in conventional gm-C filter over the temperature range of -40 to 120 degC. The variation across process corners is 2.4% and is almost independent of the capacitor variation due to process and temperature.