**How to Create a Sine (AC) Source SPICE Model**

Modeling designs helps engineers verify whether their circuit will function as intended. Modeling programs simulate circuit behavior under different conditions and in accordance with the design requirements, allowing engineers to better plan and build circuits.

Every SPICE simulation needs to have a source or input signal. To analyze how the circuit will behave in real life, this input must be modeled accurately. If not modeled accurately, functionality issues can go undetected until far later in the design process, wasting time and money. To efficiently and accurately model a sine source, the intended input signal must be interpreted by identifying the type and signal values for replication.

**What is a Sine Source**

A sinusoidal (sine) source produces a voltage that varies as a sine wave with time. There are 3 types of sinusoidal sources: sine and cosine (time domain) and AC source (frequency domain).

**What is needed to Model a Sine Source**

To create the required Sine source for simulation, there are three items that must be defined:

● Type

○ Which type of signal will be the input for the circuit: voltage or current?

● Waveform

○ What type of waveform is required: Sine, Cosine, or AC? This is dependent on the type of analysis being performed.

● Data Points

○ What are the critical signal values to create the desired waveform?

This information must be incorporated into the SPICE simulation model which can be achieved by manually creating or editing a text file. Keep in mind if the source signal created is not the intended outcome, values will need to be edited manually. This manual process to produce the desired source signal is time consuming and increases the likelihood of errors; however, the PSpice Modeling App provides a fast, easily-configurable, and fully-integrated method to create sine sources for simulation.

**PSpice Modeling App**

The Sine source modeling application quickly creates various Sine source models with a wizard-based approach. The necessary source specifications are pre-defined and users can easily input desired parameters required for all Sine sources such as:

● Type: Select either a Voltage or Current

● Waveform: Easily select from Sine or Cosine for analysis in the time domain or AC Source for analysis in the frequency domain.

● AC and DC : Quickly specify the AC or DC voltage amplitude to be automatically added to source, achieving the intended AC sweep, bias point, or transient analysis.

Based on the waveform type selected, the PSpice Modeling Application automatically defines the required parameters. For analysis in the time domain, easily define the following parameters for Sine and Cosine waveforms:

● Offset: Specify the DC offset for the waveform.

● Amplitude: Define the peak voltage or current amplitude of the sine wave.

● Frequency: Define the frequency of the sine wave in Hz.

● Delay: Define a delay to have the sine waveform begin at a specified time.

● Phase: Specify the phase of the Sine wave. When selecting Cosine the phase is automatically populated with a value of 90.

● Damping Factor: Define the damping coefficient of the sine wave to specify if the signal decays.

Using the inputted information above, the PSpice Modeling App generates a schematic symbol and automatically associates the newly created Sine source SPICE model without leaving the OrCAD Capture environment. The PSpice Modeling App also automatically manages the simulation profile configuration, eliminating any library set up for simulation. To try this yourself, be sure to download the Free Trial of OrCAD and check back for more SPICE model how-tos in this series.