A macromodel for operational amplifiers with adjustable offset voltage

Many kinds of operational amplifiers (opamp) macro-models (A. Maxim and D. Andreu, Proc. IEEE Int. Symp. on Circuits and Sys., vol. 4, p. 697-700, 2000) have been proposed to help designers to simulate and verify system behaviors, but their offset voltage could not be adjusted by external elements, which are widely applied in signal detection. A simple macro-model is proposed in this paper, and the offset voltage could be easily modulated by external resistors. As an example, UC1543, a power supply supervisory chip, has been modeled and simulated by Saber, the results show that the proposed macro-model is very accurate and convergent.