The most commonly used simulator type in MPLAB® Mindi™ Analog Simulator is the SIMetrix simulation. This article shows you how to set up a common simulation analysis (DC and AC) using SIMetrix.

Setting Up a SIMetrix Simulation

To choose simulation analysis type and settings, select Simulator > Choose Analysis or press F8. The Choose Analysis dialog box appears.

To set up the Analysis Mode, for example, Transient, AC, DC Sweep, etc. check the box on the right according to the analysis you want to perform. You can select more than one. The following describes the most commonly used analysis modes:

Transient Analysis

Your circuit is simulated over a fixed time interval, in steps of varying sizes, according to circuit activity. The circuit may contain any number of time-varying voltage and current sources to simulate external signals, test generators, etc. Usually, you only need to specify the Stop time at the top of the dialog box.

DC Sweep Analysis

A DC Device Sweep will sweep a specified device over a defined range and compute the DC operating point of the circuit at each point. This allows, for example, the DC transfer function of the circuit to be plotted. Note that all reactive elements are ignored in the DC Sweep. To set up a DC Sweep, select Simulator > Choose Analysis, check DC Sweep box under Analysis Mode at the right, then select the DC tab at the top. You will need to enter some values in the Sweep parameters section, for example:

The simulator will sweep the device you specify in the Device name box over the range specified by the Start value, Stop value, and Number of points or Points per decade if you select Decade Sweep. The entry in the Device name box is the part reference of the device to be swept which is usually a voltage source, a current source, or a resistor. Device Sweep is one of the five modes (Device, Parameter, Model Parameter, Temperature, and Monte Carlo) available with DC sweep. The Define button allows you to specify one of the others.

AC Frequency Sweep Analysis

An AC Frequency Sweep calculates the small-signal response of a circuit to any number of user-defined inputs over a specified frequency range. The small-signal response is computed by treating the circuit as a linear circuit about its DC operating point. There must be at least one input source for AC analysis for the results to be meaningful. Connect a voltage or current source to the circuit, select it, and then press F7 (when a device is selected, its color changes from red to blue). In the dialog box, check Enable AC.

Using voltage source as an example, an AC input voltage source will look something like this:

To set up an AC Frequency Sweep, select the AC tab at top and check AC on the right under Analysis Modes. You need to enter some values in the Sweep parameters section.

The analysis will sweep the frequency over the range specified by Start frequency, Stop frequency, and Points per decade if you select a Decade Sweep. Frequency sweep is one of the six modes (Device, Parameter, Model Parameter, Temperature, Frequency, and Monte Carlo) available with AC sweep. The Define button allows you to specify one of the others.