Design issues for UHF OTA-C filter realizations

Design considerations for ultra-high frequency OTA-C filters are discussed. The effects of the OTA non-idealities on the precision of high-Q filters are accounted for. The parasitic capacitors produce center frequency deviations, and the finite OTA output resistance reduces the Q-factor while the parasitic poles introduce Q-enhancement. In this paper it is shown that the non-dominant pole effects are the most critical ones, hence the use of single-stage OTA's is a must. The effects of the parasitic capacitors on the filter's linearity are considered as well. Simulated results for a 2/sup nd/ order 500 MHz high-Q bandpass filter using a 0.35 /spl mu/m technology are reported.