Basic EMC (Electromagnetic Compatibility) Technology Advancement for C3 Systems. Volume 1. A Nonlinear Macromodel of the Bipolar Integrated Circuit Operational Amplifier for Electromagnetic Interference Analysis.

Abstract : A macromodel containing two transistors can accurately predict how amplitude modulated RF signals with RF carrier frequencies in the 0.05 to 100.0 MHz range are demodulated in bipolar operational amplifiers (micro A741 and LM10 op amps) to cause undesired low frequency responses related to the modulation envelope of the RF signals. The original op amp macromodel which was developed by Boyle at al was modified by adding four capacitors C(sub) to account for parasitic capacitance effects in integrated circuit op amps. A procedure for assigning C(sub) values is given. The macromodel can be used when the RFI signals are incident upon the op amp input terminals. The use of the macromodel leads to a substantial reduction in computer time and expense. The ability of the nonlinear macromodel to represent the overall integrated circuit nonlinear response with only two transistors at the input stage is explained using the feedback theory of cascaded nonlinear transfer functions. In an operational amplifier with a linear feedback in its second stage, the nonlinear response of the second stage is suppressed. The overall nonlinear response is dominated by the nonlinearities of the input stage. (Author)