3.1 Introduction

The recent research interest in integrated active LC filters on silicon [1 6] can be largely attributed to:

• the advent of highly integrated wireless communication transceivers. This provides potential applications for integrated active LC filters, since on-chip spiral inductors can have usable Q and inductance in the GHz frequency range. While at present the noise of active LC filters is not sufficiently low to allow their use in receivers, it may be sufficiently low for certain applications in transmitters, e.g. to clean up the signal following a mixing operation.

• persistent efforts to improve the quality of on-chip spiral inductors. Not only can the physical layout of the inductors be optimised with the aid of computer simulators [7 9], but some processes have been tailored to produce high- Q spiral inductors [10 12]. As a result, spiral inductors with values of several nH and Q of more than 6 in the 1 5 GHz frequency range have become practically available on silicon chips.

• the achievable superior dynamic range ^[2] (DR) performance of active LC filters compared to that of other integrated continuous-time filters not using inductors [2, 14]. The DR of active LC filters can be further increased with the improvement of the quality of on-chip reactive components.

Integrated active LC filters are not simply copies of their discrete counterparts. The difficulty of integration mostly results from two problems:

1. Reactive components integrated on silicon are more nonideal than the corresponding discrete parts. Such integrated...