A log-domain CMOS transcapacitor: Design, analysis and applications

We present in this paper the CMOS implementation of a transcapacitor workin g in the log-domain. This circuit integrates a differential input current i nto an output pseudo-voltage, which is similar to the compressed voltage us ed as the internal variable in companding filters. This log-domain transcap acitor is compatible with pseudo-conductances implemented with a single tra nsistor. The pseudo-transcapacitor circuit is analyzed and a collection of log-domain reactive components and small circuits using it is proposed.