PSpice User Guide

PSpice User Guide

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PSpice User Guide Analog behavioral modeling October 2019 362 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. Frequency-domain device models Frequency-domain models (ELAPLACE, GLAPLACE, EFREQ, and GFREQ) are characterized by output that depends on the current input as well as the input history. The relationship is therefore non-instantaneous. For example, the output may be equal to the integral of the input over time. In other words, the response depends upon frequency. During AC analysis, the frequency response determines the complex gain at each frequency. During DC analysis and bias point calculation, the gain is the zero-frequency response. During transient analysis, the output of the device is the convolution of the input and the impulse response of the device. Moving back and forth between the time and frequency-domains can cause surprising results. Often the results are quite different than what one would intuitively expect. For this reason, we strongly recommend familiarity with a reference on Fourier and Laplace transforms. A good one is: ■ R. Bracewell, The Fourier Transform and Its Applications, McGraw-Hill, Revised Second Edition (1986) We also recommend familiarity with the use of transforms in analyzing linear systems. Some references on this subject: ■ W. H. Chen, The Analysis of Linear Systems, McGraw-Hill (1962) ■ J. A. Aseltine, Transform Method in Linear System Analysis, McGraw-Hill (1958) Laplace transforms (LAPLACE) The ELAPLACE and GLAPLACE parts allow a transfer function to be described by a Laplace transform function. The ELAPLACE and GLAPLACE parts are defined, in part, by the following properties (default values are shown): ELAPLACE EXPR V(%IN+, %IN-) XFORM 1/s

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