DESIGN AND IMPLEMENTATION OF CURRENT MODE FILTERS USING LOG DOMAIN TECHNIQUES

Abstract

Due to the ongoing trends of lower power supply voltages and low power operation, the area of analog integrated filters is facing challenges. The maximal dynamic range achievable through conventional filter implementation techniques such as OA (Operational amplifier), MOSFET-C, transconductance-C etc. are restricted by the supply voltage. With log domain filters having signal swing of 100 mV, we can achieve 60-80 dB of dynamic range in circuits operating in the MHZ range using power supplies of 2.5V or less. These features make them an interesting choice in signal processing applications. Log-domain filters have emerged in recent years as a new and important class of Current-mode circuits The present works deals with the signal processing applications of the log domain circuits. After presenting an overview of the log domain filtering, translinear principle for log domain filters, Bernoulli cell and its implementation to higher order filters have been presented. In the later part, design of log domain filters based on operational simulation of LC ladders and state space synthesis have been presented. All the circuits presented in the dissertation have been simulated in PSPICE.