SCMOS: a software tool for studying the behavior of analog MOS integrated circuits

The study of analog integrated circuits can be carried out at several levels, from the structure and operation of their basic building blocks to the design methodologies. At any of these levels there is a need for tools that allow the influence of design parameters in the behavior of the circuits to be clearly shown to the students. This paper presents a software tool, namely SCMOS, that allows the functional characteristics of an analog MOS circuit (gain, bandwidth, etc) and their variations due to the modification of design parameters (lengths and widths of transistors, parasitic capacitances, etc) to be checked. Different analyses (transients, AC and DC sweeps) can be performed and their results can be checked in the form of parametric curves, on which the correspondences between parameter variations and functional characteristic variations can be viewed. SCMOS allows a predefined set of topologies, ranging from single-transistor stages to operational amplifiers, to be studied but other topologies can be easily added.