Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice A/D User Guide AC analyses October 2019 510 Product Version 17.4-2019 © 2022 All Rights Reserved. How PSpice A/D 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 A/D does PSpice A/D automates this process for you. PSpice A/D 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 A/D needs a known bias point.