Synthesis of Log-Domain Filters from First-Order Building Blocks

Log-domain filters are an important class of current-mode circuits having large-signal linearity and increased tuning range over voltage-mode filter circuits of similar complexity. In this paper we describe synthesis of a single-ended, first-order filter circuit from static and dynamic translinear circuit principles, and show how higher-order filters can be easily constructed from the first-order building block. We address additional issues related to low-frequency (audio-frequency) filter design and present results measured from test circuits and a complete 15-channel filterbank system fabricated in 2 m and 1.2 m BiCMOS processes.