Synthesis of distortion compensated log-domain filters using state space techniques

A new state space method is proposed for the synthesis of "quasi-log domain" filters where the parasitic emitter resistance of transistors is built into the equation formulation. The explicit exponential maps for log domain filters are replaced with implicit exponential maps yielding modified nodal equations for active filters. Circuit realization is discussed and some example circuit topologies are proposed. Finally, the extension to general higher order filters is suggested.