Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide AC analyses October 2019 498 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. How PSpice treats nonlinear devices An AC Sweep analysis is a linear or small-signal analysis. This means that nonlinear devices must be linearized to run the analysis. What's required to transform a device into a linear circuit In order to transform a device (such as a transistor amplifier) into a linear circuit, you must do the following: 1. Compute the DC bias point for the circuit. 2. Compute the complex impedance and/or transconductance values for each device at this bias point. 3. Perform the linear circuit analysis at the frequencies of interest by using simplifying approximations. Example: Replace a bipolar transistor in common-emitter mode with a constant transconductance (collector current proportional to base-emitter voltage) and a number of constant impedances. What PSpice does PSpice automates this process for you. PSpice computes the partial derivatives for nonlinear devices at the bias point and uses these to perform small-signal analysis. Example: nonlinear behavioral modeling block Suppose you have an analog behavioral modeling block that multiplies V(1) by V(2). Multiplication is a nonlinear operation. To run an AC sweep analysis on this block, the block needs to be replaced with its linear equivalent. To determine the linear equivalent block, PSpice needs a known bias point.