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How to Create AND and NAND Gate SPICE Models

Modern electronics could not exist without semiconductors and digital electronics but as electronics become faster and more complex, it’s essential to model realistic behavior to ensure design accuracy. At high speeds, digital electronics are susceptible to issues with propagation delay, and any stray capacitance present on the board could lead to attenuation, which could prevent a high input from ever reaching the device’s threshold voltage. PSpice allows you to quickly create custom AND and NAND Gate SPICE models for accurate simulation of digital designs with a wizard-based approach.

This quick how-to will provide step-by-step instructions on how to create accurate AND and NAND gate SPICE models with the Modeling Application in OrCAD PSpice.

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

How-To Video

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Creating an AND Gate SPICE Model

Step 1: Open the provided design in OrCAD PSpice 23.1.

Note: A wizard-based approach to digital models is new in version 23.1. See other new features here.

Activating the Modeling Application in PSpice

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

Step 3: In the Modeling Application, expand Digital > Gates.

Step 4: Select AND/NAND.

Using the Modeling application in PSpice to create an AND Gate SPICE Model
Configuring AND Gate SPICE Model Parameters

Step 5: In the resulting options window, ensure the following logic parameters are configured:

  • Number of Inputs: 2
  • Number of Outputs: Q
  • Inverted Inputs: 0

Step 6: Enter the following model parameters:

  • Propagation Delay: 7.9n
  • Threshold: 1.4
  • Hysteresis Width: 1.2
  • Output Resistance: 1m
  • Input Resistance: 10G
  • Max High Voltage: 5

Note: The logic device being modeled has negligible output resistance and requires negligible input current.

Step 7: Click Place.

Step 8: Click to place the AND gate in the schematic.

Step 9: Select the Voltage/Level Marker button from the toolbar.

Placing a Probe in PSpice

Step 10: Click to place a probe at the output of the gate. Right-click and select End Mode.

Running the Simulation

Step 11: Select PSpice > Run from the menu.

Step 12: View the results.

Creating a NAND Gate SPICE Model

Step 13: Back in the schematic, select the AND gate and press Delete on the keyboard.

Step 14: Select Digital > Gates > AND/NAND from the Modeling Application.

Using the Modeling Application in PSpice to create a NAND Gate SPICE Model
Configuring NAND Gate SPICE Model Parameters

Step 15: Set the Number of Outputs to Qbar to invert the output.

Note: Selecting Both as the Number of Outputs will create a gate with a non-inverted and inverted output.

Step 16: Enter the following model parameters:

  • Propagation Delay: 9.7n
  • Threshold: 1.25
  • Hysteresis Width: 0.75
  • Output Resistance: 1m
  • Input Resistance: 10G
  • Max High Voltage: 5
Placing a NAND Gate in PSpice

Step 17: Click Place. Click to place the gate in the schematic.

Step 18: Select PSpice > Run from the menu.

Step 19: View the results. The output is inverted.

Wrap Up & Next Steps

Quickly create the required AND or NAND gate SPICE model and simulate accurate digital circuit behavior with the PSpice Modeling Application in OrCAD PSpice. Upgrade to the latest 23.1 release or test out this feature and more with a free trial of OrCAD.

Follow Along, Download the Pre-Packaged Design Files

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