Design of log domain differential class AB universal biquad filter by employing lossy integrators

Abstract

A new current mode low voltage differential Class AB second order universal biquad filter has been designed in this work. In design process, inspiring from Kerwin-Huelsman-Newcomb circuit, the circuit is realized with lossy integrators. The circuit has fundamental filter outputs namely; low pass, high pass and band pass. All pass and notch filter outputs have also been obtained by using additional circuits. In circuit design process, the state space method and translinear principle have been used. Two of the circuit parameters are electronically tunable which are the quality factor Q and the pole frequency f₀. PSpice circuit simulations have been obtained to check the theoretical results’ validity. In PSpice simulations, both ideal and AT&T CBIC-R type real transistor models have been used.