Design of the third order elliptic filter with seevinck type dummy inputs in the log domain using the state space synthesis method

Abstract

In this paper, a current mode, third order, elliptic filter is synthesized in the log domain. The state space synthesis method is used for the design procedure. Seevinck type dummy inputs are used in order to realize a Class AB and differential type elliptic filter for the first time. Initially, ideal transistors with infinite forward gain are used for PSpice simulations in order to verify the validity of the mathematical derivations. The AC response of the filter was as predicted. Using CBIC-R type real transistors, the simulations are repeated. Some minor differences between ideal and real transistors' responses are observed and the results are discussed. On the other hand, for the time domain analysis, the circuit is driven by a signal at the filter's comer frequency, i.e. f=100 kHz. This response was also as predicted. © 2005 IEEE.