The George Washington University School of Engineering and Applied Science Department of Electrical and Computer Engineering Circuit Design Verification Using PSpice (Cadence/OrCAD) Jason Woytowich (former GTA) Farid Hassani (ECE GTA)

Outline Introduction General Process Basic Example – Half-Wave Rectifier Advanced Example – Demodulation

Introduction SPICE is a general purpose circuit simulation language that performs non-linear DC, transient and linear steady state AC analysis. SPICE models: –Linear circuit elements of resistance, capacitance, inductance, independent and dependent current and voltage sources –Four of the most common nonlinear semiconductor devices (Diodes, BJTs, JFETs and MOSFETs) –Other useful circuit elements including transmission lines and mutual inductance

Cadence PSpice OrCAD bought MicroSim and its PSpice products in January Cadence bought OrCAD in August 1999.

General Process 1. Design your circuit 2. Draw your circuit 3. Specify your analysis 4. Run the simulation 5. Analyze the output 6. Go back to 1, 2 or 3 as needed

Starting Cadence

Start a New Project

Select Project Options

Project Types Only two types are of immediate concern 1.Analog or Mixed A/D -The project is meant for simulation. This is for design verification. 2.Schematic -This option is used for PCB design. It is only used to generate a netlist. We will use this for your Board Fabrication Details.

Create a Blank Project

Schematic

Place Parts

Placing Parts

Changing Values

Completed Half-Wave Rectifier

Create a Simulation Profile

Set the Simulation Parameters

Simulation Types DC / OpPoint – All AC sources are zeroed (Shorted/Opened) Transient – View with respect to time DC Sweep – View the response to a range of DC inputs AC Sweep – View the response to a range of frequencies

Run the Simulation Press the blue arrow in the toolbar on the top.

Select Output

Output 1

More Output

Output 2

A More Complicated Example Input – 5Vpeak, 2kHz Sine Wave pulsed for 5ms ever 20ms starting 1ms and an output impedence of 1kOhm The input passes through a simple BPF with a gain of 1. The output of the BPF is rectified and passed through an RC filter with a time constant of 0.5ms. Put the output across a 1Meg Ohm resistor.

Using Heirarchy You can break your Pspice design into modules. These modules can be linked together at the top level.

Signal Source VDC VSI N VPULS E MULT – From ABM

Band Pass Filter LM741 from OPAMP Notice the power supply connections Input Port Output Port

Rectifier

Top Level

Simulation Is the output what you expect?

Simulation

Perform Your Own Simulations This presentation was adapted from a presentation by Farid Hassani