A new biquad circuit realizing high-order MOSFET-C filters

The MOSFET-C continuous-time biquadratic building block proposed by A.E. Said et al. (1991) does not realize all generic transfer functions. When implemented in a high-order realization, it requires the addition of unity gain inverters. A new biquad circuit is proposed to overcome the above problems. It achieves a complete MOS nonlinearity cancellation and does not require the use of fully balanced op amps. An example of a second-order biquad filter is analyzed using SPICE. A high-order implementation of the proposed biquad is also given. All design steps are matched with the 3.3-μm CMOS design rules