State-space synthesis of a first-order differential class-AB log-domain allpass filter

Abstract

A first-order differential type class-AB log-domain filter is proposed. It is systematically derived using the state-space synthesis procedure. To the best knowledge of the authors, the filter is the first log-domain first-order allpass filter in the literature. PSPICE simulations are performed using both, Bipolar Junction Transistors (BJT) and ideal devices to confirm the theoretical analysis. The small deviations in the gain and phase response from theoretical values are caused by the non-idealities of the BJT such as finite-beta, non-zero ohmic junction resistances, Early voltages. © 2005 IEEE.