The Small-Signal Distortion analysis computes steady-state harmonic and intermodulation products for small input signal magnitudes. If signals of a single frequency are specified as the input to the circuit, the complex values of the second and third harmonics are determined at every point in the circuit. If there are signals of two frequencies input to the circuit, the analysis finds out the complex values of the circuit variables at the sum and difference of the input frequencies, and at the difference of the smaller frequency from the second harmonic of the larger frequency.

Distortion analysis is supported for the following nonlinear devices: diodes, BJT, JFET, MOSFETs (levels 1, 2, 3, 4/BSIM1, 5/BSIM2, and 6) and MESFETS. All linear devices are automatically supported by distortion analysis. If there are switches present in the circuit, the analysis continues to be accurate provided the switches do not change state under the small excitations used for distortion calculations.

For more information on Distortion analysis, see the .DISTO instruction in the Simulator Reference Guide.

# Description

Enter a brief description of the type of analysis. The text entered is the title of the document in which the simulation results will be stored.

# Analysis Range

In this section, you must specify the frequency range for which the analysis is to be performed.

## Sweep Type

Defines how test points are determined within the specified frequency range.

**Linear sweep.**The frequency is swept linearly from Start frequency to Stop frequency for the total number of values indicated in Number of points.**Sweep by decades.**The frequency is swept logarithmically by decades between the Start Frequency and Stop Frequency. For each interval, the number of values specified by Number of points is taken. The extremes of the intervals are such that*extreme2=10*extreme1*. For example, if you specify 1K for the initial value, 1Meg for the final value and 10 for number of points. The analysis interval is divided into three sub-intervals and the values are taken, on a logarithmic scale, as ten for each interval.**Sweep by octaves.**The frequency is swept logarithmically by octaves between Start frequency and End frequency. For each interval, the number of values specified by Number of points is taken. The extremes of the intervals are such that*extreme2=2*extreme1*. For example, if you specify 1K for the initial value, 1Meg for the final value and 4 for number of points. The analysis interval is divided into ten sub-intervals and the values are taken, on a logarithmic scale, as four for each interval.

## Start Frequency

The initial frequency for the sine wave generator (in Hz).

## Stop Frequency

The final frequency for the sine wave generator (in Hz).

## Number of Points

Specifies the number of points to be analysed. If the frequency varies linearly, this parameter specifies the total number of points otherwise it indicates the number of points to be analysed for each decade or octave.

# Sources

Lists all voltage and current sources in the circuit. The values for the parameters DISTOF1 and DISTOF2 are shown for each source. The DISTOF1 parameter specifies that the source has a distortion at the frequency F1. The DISTOF2 parameter specifies that the source has a distortion at frequency F2.

The amplitude followed by the value of the phase (in degrees) must be specified. If the phase is not specified, a null phase is assigned.

# f2/f1

A number greater than zero and less than 1. Determines the type of analysis. If this parameter is not specified or if its value is zero, a harmonic analysis is performed, otherwise a spectral analysis is performed.

If the parameter F2/F1 is missing or if its value is zero, a harmonic analysis of the circuit is carried out at the frequency F1, which is made to vary according to the specified parameters. The sources are made up of all the independent generators for which the DISTOF1 parameter has been specified. The analysis produces the values of the voltages at the nodes and the currents in the circuit at the harmonic frequencies 2F1 and 3F1 with respect to the input frequency F1.

If a value is specified for the parameter F2/F1, a spectral analysis is performed considering sinusoidal signals at the frequencies F1 and F2 as input. F1 is varied according to the specified parameters while F2 is set to Start_Frequency*F2/F1. The sources for F1 are made up of all the independent generators for which the parameter DISTOF1 has been specified while the sources for F2 are made up of all the independent generators for which the parameter DISTOF2 has been specified. The analysis produces the values of the voltages at the nodes and the currents in the circuit at the intermodulation frequencies F1 + F2, F1 - F2 and (2F1) - F2 with respect to the input frequency F1.

# Temperature

Specify the temperature at which the simulation will be performed.

# Analysis Mode

Specify whether a single or multiple analysis should be performed. The
multiple analysis performs several consecutive simulations, varying the
value of some parameters at each step. When a multiple analysis is
selected, the **Setup** button is activated. Click on the
button to activate the dialog in which to set the specific parameters
for the selected analysis mode.

The following analysis modes are supported, click a link to learn more about that analysis mode:

# Collect Data For

Specifying the simulation data to be collected. Simulations, especially multiple simulations, can produce a large amount of data, causing excessive memory usage and lower simulation speed. This section allows you to specify which information resulting from the simulation should be stored. Select one of the following options:

**Voltages, Currents, Probes**: Saves data for the voltage at each node and the current in each supply in addition to the signals specified via the Probe objects included in the schematic.**Voltages, Currents**: Saves data for the voltage at each node and the current in each supply;**Signals specified by Probe objects**: Stores only the signals specified via the Probe objects included in the schematic.**The specified signals**: To reduce the amount of data stored during a simulation it may be convenient to specify the names of only the vectors of interest, in this case only the data relating to the specified vectors will be stored. When this option is selected, the**Setup**button is activated; click on the button to activate the Vectors dialog box in which to specify the names of the vectors.

# Options

Click on this button to activate the dialog box in which to set the options of the simulator. The options set are only valid for the current analysis and replace those defined in the general tab of the simulator options.

# Plot

Click on this button to activate the dialog box in which to set the diagrams and the list of vectors to be included in the diagrams. See the Plot dialog box.