Nonideality Analysis of Biquadratic Log-Domain Filters

Summary

Simple formulae that account for log-domain integrator errors due to major transistor nonidealities (such as parasitic emitter and base resistances, finite ß , Early voltages, and area mismatches) were derived. They can be used to predict the frequency response deviations experienced by lowpass or bandpass biquadratic filters. Simplifying assumptions were made to tackle the log/exp transcendental nature. Nevertheless, the resulting predictions are practical, and their accuracy have been confirmed by SPICE. Finally, several simple electronic compensation schemes were proposed to correct for these transistor nonidealities.