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How to Create a Voltage-Controlled Oscillator SPICE Model

Voltage-controlled oscillators are an important tool when testing circuits such as FM demodulators, filters, and audio processors and equalizers; however, accurately creating the corresponding SPICE model can be time-consuming. With PSpice you can quickly create the required Voltage-Controlled Oscillator (VCO) SPICE model to create a realistic simulation by easily defining the type and signal value.

This quick how-to will provide step-by-step instructions on how to create a voltage-controlled oscillator SPICE model in OrCAD PSpice.

To follow along, download the provided files above the table of contents.

How-to Video

Creating a Voltage-Controlled Oscillator SPICE Model

Step 1: Open the provided design in OrCAD PSpice Designer.

Step 2: Select Place > PSpice Part > Modeling Application from the menu.

Creating a VCO SPICE Model in PSpice

Step 3: In the Modeling Application, expand System Modules and select VCO.

Step 4: The PSpice Modeling Application VCO window opens. Select the VCO – Sinusoidal radio option to generate a sinusoidal VCO.

Note: A triangular or square wave VCO can be created as well.

Defining VCO SPICE Model Parameters in PSpice

Step 5: Set the Maximum Operating Frequency to 1.5k and the VCO Sensitivity to 140.

Learn how to decipher a VCO datasheet to determine the parameters required for SPICE Model creation here.

Note: Additional options can be set for minimum operating frequency, maximum controlling voltage, and initial phase.

Step 6: Click Place to attach the source to your cursor.

Placing VCO SPICE Models in PSpice

Step 7: Click to place the source in the schematic.

Running the Simulation

Step 8: Select PSpice > Run from the menu.

Viewing the Simulation Results

Step 9: View the simulation results. As the control voltage V(VCTL) increases, the input and output frequencies increase.

Modifying the Voltage-Controlled Oscillator SPICE Model

Step 10: Back in the schematic, select the VCO and press Delete on the keyboard.

Step 11: Select System Modules > VCO in the Modeling Application.

Configuring the VCO SPICE Model Parameters

Step 12: Set the Maximum Operating Frequency to 3k and the Minimum Operating Frequency to 1k.

Step 13: Click Place to attach the source to your cursor.

Step 14: Click to place the source in the empty space.

Step 15: Select PSpice > Run from the menu.

Step 16: View the simulation results. The VCO output frequencies are higher, and the output cuts off at higher frequencies.

Wrap Up & Next Steps

Quickly create the required Voltage-Controlled Oscillator SPICE model and simulate accurate circuit behavior with the modeling application in OrCAD PSpice. Test out this feature and more with a free trial of OrCAD.

To learn more about deciphering a VCO datasheet to determine the parameters required for SPICE Model creation, view our blog here.

Follow Along, Download the Pre-Packaged Design Files

Table of Contents

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