A high-selectivity switched-capacitor bandpass filter

A high-selectivity switched-capacitor bandpass filter is presented. The filter center frequency is 100 kHz with a -3 dB bandwidth of 980 Hz (i.e., with a quality factor Q similar to 100), This has been implemented with a 12th-order transfer function whose poles are placed at only two frequencies. This choice has been used in the integrated circuit realization. In fact, the transfer function has been implemented using the cascade of six biquad cells of only two types. For the available 20 samples, the center frequency mean-value error is lower than 0.2%, and the Q mean-value error is lower than 0.2% as well. The filter is realized in a not-recent BICMOS technology (L-NMOS = 4 mum, L-PMOS = 3 mum) The same performance (opamp, switches, and overall filter) can be easily obtained with a standard scaled-down (0.35 mum, for instance) CMOS technology, In this direction, an evaluation of the area and power consumption of the circuit as implemented in a standard 0.35-mum CMOS technology is finally given.