A design methodology for analogue CMOS circuits

ABSTRACT

The design of CMOS analogue circuits calls for the appraisal of transistor geometries and currents to meet prescribed specifications like gain-bandwidth, min. power consumption, etc. Design methodologies to this effect are scarse. Often they resume to cautiously chosen simulations performed by experienced designers.The objective of the tutorial is to propose a design methodology based on the transconductance over current ratio. Synthesis is performed following a path that attempts to make the best possible use of existing degrees of freedom in order to come close to 'optimal' transistor sizes and currents. The methodology is applied to some examples like the sizing of an Operational Amplifier, which combines transistors operating in strong inversion for matching and moderate inversion to lessen the power consumption.