Impact of OTA nonlinearities on the performance of continuous-time OTA-C bandpass filters

A new technique for predicting actual large-signal frequency responses, including jump resonance, in high-Q bandpass filters constructed from OTAs (operational transconductance amplifiers) and linear capacitors is presented. These predictions are a function of the nonlinearities of the OTAs and the Q enhancement of the filter. This approach offers significant advantages over other published techniques: a closed-form expression is obtained which is used to estimate the sensitivity of the nonideal filter parameters to signal amplitude, OTA distortion and Q enhancement, and which offers valuable insight into the nonideal operation of the filter. A representative filter structure is discussed. It shows close agreement between measurement and predicted responses in the presence of both Q enhancement and QTA distortions