High-linearity continuous-time filter in 5-V VLSI CMOS

High-linearity self-tuning continuous-time filters, fabricated in a standard 1.6-μm 5-V CMOS process, are presented. Frequency control is achieved using switchable arrays of highly linear double-polysilicon capacitors in an active RC filter structure, resulting in tunable filters with very low signal distortion. One filter, a Tow-Thomas biquad, exhibits dynamic range and signal linearity of typically 91 dB. Another smaller implementation, a Sallen and Key filter, attains ⩾76 dB. Cutoff frequency response is maintained to an accuracy of around ±5%