Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide Monte Carlo and sensitivity (worst-case) analyses October 2019 594 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. ■ a worst-case analysis (shown disabled in the circuit file) that allows PSpice to determine the worst-case value for parameter R based upon a sensitivity analysis. Only one of these analyses can run in any given simulation. Note: The AC and worst-case analysis specifications (.AC and .WC statements) are written so that the worst-case analysis tries to minimize Vm([OUT]) at 100 kHz. The netlist and circuit file in Figure 13-11 are set up to run either a parametric (.STEP) or worst-case (.WC) analysis of the specified AC analysis. These simulations demonstrate the conditions under which worst-case analysis works well and those that can produce misleading results when output is not monotonic with a variable parameter (see Figure 13-15 and Figure 13-16). For demonstration, the parametric analysis is run first, generating the curve shown in Figure 13-15 and Figure 13-16. This curve, derived using the YatX measurement shown in Figure 13-12 illustrates the non-monotonic dependence of gain on Rb2. Figure 13-13 YatX Measurement Expression To do this yourself, place the measurement definition in a PROBE.PRB file in the circuit directory. Then start PSpice, load all of the AC sweeps, set up the X axis for performance analysis, and add the following trace: YatX(Vm([OUT]),100k) Note: The YatX measurement is used on the simulation results for the parametric sweep (.STEP) defined in Figure 13-11. The resulting curves are shown in Figure 13-15 and Figure 13-16. Next, the parametric analysis is commented out and the worst-case analysis is enabled. Two runs are made using the two versions of the Rbmod .MODEL statement shown in the circuit file. The model parameter, R, is a multiplier which is used to scale the nominal value of any resistor referencing the Rbmod model (Rb2 in this case). YatX(1, X_value)=y1{1|sfxv(X_value)!1;}