Log-domain CMOS transcapacitor: Design, analysis and applications

We present in this paper the CMOS implementation of a transcapacitor working in the log-domain. This circuit integrates a differential input current into an output pseudo-voltage, which is similar to the compressed voltage used as the internal variable in companding filters. This log-domain transcapacitor is compatible with pseudo-conductances implemented with a single transistor. The pseudo-transcapacitor circuit is analyzed and a collection of log-domain reactive components and small circuits using it is proposed.