A new approach to the design of operational amplifier macromodels, based on a multi-terminal non-linear equation defined device, is presented. The concept of a compact macromodel is introduced and demonstrated by the design of a general purpose operational amplifier macromodel. The new macromodel models the principle operational amplifier characteristics, plus a number of features not normally found in previously published macromodels, including common-mode range, differential gain reduction during output voltage saturation, power-supply current sensing and temperature effects. The performance of the new macromodel has been tested using the Qucs circuit simulator and has been found to perform well in comparison to other published operational amplifier macromodels.