Computer-aided analysis of electronic circuits—the need to include parasitic elements† ‡

Models for the fundamental passive electrical components (R, C, L) which include the dominant parasitic elements are shown. Typical values for the parasitic elements are given. A procedure for using computer-aided design (CAD) simulation programmes such as SPICE 1 to estimate the effects of parasitic elements on electronic circuit performance in the HF/VHF region is described. As an example to demonstrate the usefulness of this procedure a linear model was presented for an audio frequency junction field effect transistor (AF JFET) amplifier suitable for RFI analysis at high frequencies. The CAD simulation and the experimental results for the amplifier voltage transfer ratio in the 0.1 to 100 MHz frequency range were observed to be in good agreement when typical parasitic element values were used. By adjusting the initial (typical) parasitic element values, the agreement between calculated and experimental results can be improved.