Yichuang Sun

No matter to what extent digital techniques are used, analogue filters will always be needed for interfacing the real analogue world. Also, in recent years, the renewed interest in analogue, mixed-signal and RF circuits due to system-on-chip design has led to a new peak of research of high frequency integrated analogue filters. In fact, the high frequency integrated analogue filter has become a key component in achieving ubiquitous communication and computing. This book has been concerned with this fast growing area. Seven advanced topics have been included, namely OTA/g _m-C filters, MOSFET-C filters, active LC filters, log domain filters, switched current filters, analogue adaptive filters, and on-chip automatic filter tuning.

Whilst traditional active RC filters utilise the high gain operational amplifier in closed loop form, OTA/g _m-C filters dominating high frequency applications use the tunable transconductance amplifier in open loop form and do not use resistors. Chapter 1 has addressed the architectures, performance, design, tuning and implementation of OTA-C filters. Two integrator loop, LC ladder-based and multiple loop feedback g _m-C filters have been introduced, together with current-mode g _m-C filters. The diversity of design methods has been emphasised and guidance on choice of design for particular applications has been given, bearing in mind that each method has its own merits. Design examples using CMOS technology have also been given and automatic tuning issues have been discussed.

MOSFET-C filters result directly from active RC filters with the resistor being replaced by the tunable MOSFET.