PSpice User Guide

PSpice User Guide

Issue link: https://resources.pcb.cadence.com/i/1180526

Contents of this Issue

Navigation

Page 363 of 884

PSpice User Guide Analog behavioral modeling October 2019 364 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. TEMPLATE= E^@REFDES %OUT+ %OUT- LAPLACE {@EXPR}= (@XFORM) After netlist substitution of the template, the resulting transfer function would become: V(%OUT+, %OUT-) = LAPLACE {V(%IN+, %IN-)}= (1/1+.001*s)) The output is a voltage and is applied between pins %OUT+ and %OUT-. For DC, the output is simply equal to the input, since the gain at s = 0 is 1. For AC analysis, the gain is found by substituting j·ω for s. This gives a flat response out to a corner frequency of 1000/(2π) = 159 Hz and a roll-off of 6 dB per octave after 159 Hz. There is also a phase shift centered around 159 Hz. In other words, the gain has both a real and an imaginary component. The gain and phase characteristic is the same as that shown for the equivalent control system part example using the LAPLACE part (see Figure 6-7 on page 344). For transient analysis, the output is the convolution of the input waveform with the impulse response of 1/(1+.001·s). The impulse response is a decaying exponential with a time constant of 1 millisecond. This means that the output is the "lossy integral" of the input, where the loss has a time constant of 1 millisecond. This will produce a PSpice A/D netlist declaration similar to: ERC 5 0 LAPLACE {V(10)} = {1/(1+.001*s)} Frequency response tables (EFREQ and GFREQ) The EFREQ and GFREQ parts are described by a table of frequency responses in either the magnitude/phase domain or complex number domain. The entire table is read in and converted to magnitude in dB and phase in degrees. Interpolation is performed between entries. Phase is interpolated linearly; magnitude is interpolated logarithmically. For frequencies outside the table's range, 0 (zero) magnitude is used.

Articles in this issue

view archives of PSpice User Guide - PSpice User Guide