13.1 Introduction

The continued proliferation of mixed analog/digital VLSI systems has and will ensure that the need for small size, high speed analog-to-digital and digital to analog converters (ADCs and DACs) fabricated using commonly available digital processes will continue to grow. Initially, the widespread use of MOS technology, with its unique ability to accurately store and transfer voltages or charge packets [1], led to the development of analog integrated circuit techniques in which voltage was used as the signal. Although these techniques are quite successful in many applications, reductions in the available supply voltage and the deterioration in the performance of the analog components caused by the move to ever smaller geometries, is likely to limit their performance [2]. To address this issue, converters that do not require high quality analog components and still offer good performance with a minimum of chip area must be developed.

Current mode techniques (in which the signal is essentially processed in the current domain) offer a number of advantages. Generally current mode circuits do not require amplifiers with high voltage gains thereby reducing the need for high performance amplifiers [3]. At the same time current mode circuits generally do not require either high precision resistors or capacitors and when capacitors are used to store the signal, the capacitors need not display either good ratio matching or good linearity ^[2 ^, 4 ^, 5 ^]. Consequently, current mode circuits can be designed...