Introduction

The rapidly increasing integration densities of I.C. technologies has forced some fundamental changes of direction in the field of analog integrated electronics. For years, the circuit design almost exclusively focussed on the improvement of the signal processing properties. Demands on accuracy, offset and noise, etc., led the appearance of new circuit generations. Although these properties remain of importance today, the design emphasis has shifted from the basic qualities towards the ability of circuits to operate at a low supply voltage, consuming a minimum amount of power. The lower supply voltage leads to drastic changes in the way circuits are built up, since many of traditional circuit solutions become obsolete and need replacement.