Optimization is all about meeting requirements. In the last post, you read about how you can use measurements to optimize a circuit. This post will discuss the use of curve fitting to optimize a circuit. In this method, the goal or constraint is not a measurement, but a curve or a table of points. If you are interested in the performance of a circuit that can be best described by a waveform instead of a value, say a practical filter circuit response, curve-fitting is the choice. You can use an external specification composed of measurement data defined in an external data file when using curve fitting as an optimization goal.
You will run Optimizer on the following bandpass schematic. You can open the design from tools\pspice\tutorial\capture\pspiceaa\bandpass of your installation.
You will optimize the values of the component parameters in the circuit, such that the output waveform matches the waveform described in a reference file. For this design example, you will use a reference file to specify the waveform for the voltage gain (dB) of the output voltage (DB(V(Vout)) and the phase gain of the output voltage (P(V(Vout)). A reference file contains measured points and the corresponding measurement values. In this example, you will use a reference file named reference.txt.
To be able to run Optimizer, do the following:
To run the simulation, do the following:
To generate a reference file from PSpice, do the following:
Before running Optimizer, you must specify the component parameters and set up the curve-fit specification. Perform the following steps to do so:
You can edit the schematic to update the values suggested by the simulation.
You can view an Optimizer run because by default all runs are saved. To view a run, say run 3, for the phase of the output voltage in PSpice do the following:
You can quickly define external specifications using waveforms and reference tables and then determine the right component parameters to achieve the specification using Optimizer in PSpice Advanced Analysis. This is especially useful for any wave-shaping circuits that you might be designing.
The previous post discussed the standard, measurement-based way of specifying goals and constraints. This post takes the exploring of Optimizer one step ahead by discussing Curve Fitting, which is the curve-based method that uses points on a waveform to specify requirements. In the next post, you will be exploring another useful Advanced Analysis feature, Monte Carlo Analysis that predicts the behavior of a circuit statistically and calculates yield.
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