High temperature has a direct impact on the behavior of an integrated circuit (IC). Instrumentation and measurement circuits and systems are one of the most sensitive ICs to such working condition. Modeling the temperature impact on these systems could be achieved by many approaches. In this paper, we present an attractive method to characterize the temperature effect on an elementary circuit: the operational amplifier (op- amp). We develop a behavioral model for a commercial operational amplifier by using a set of temperature measurements of common performance parameters. As it presents several advantages, VHDL-AMS language was chosen to develop the model.