Tuning strategies in high-frequency integrated continuous-time filters

Three approaches for tuning integrated continuous-time filters are discussed and compared. Results are presented that refer, but are not limited to, second-order bandpass filters implemented with transconductance amplifiers and capacitors (OTA-C filters). It is shown that tuning with two frequencies has superior performance over single-frequency tuning: in this first case, center frequency, bandwidth, and midband gain of a biquad can be tuned exactly; in the second case, only center frequency and midband gain can be so tuned. >