The SPICE circuit simulator and models

V2.07 29-Jul-04

1. Introduction

SPICE is an acronym for Simulation Program with Integrated Circuit Emphasis and was inspired by the need to accurately model devices used in integrated circuit design. It has now become the standard computer program for electrical and electronic simulation. The majority of commercial packages are based on SPICE2 version G6 from the University of California at Berkeley although development has now progressed to SPICE3. The increased utilisation of PCs has led to the production of PSPICE, a widely available PC version distributed by the MicroSim Corporation whilst HSPICE from Meta-Software has been popular for workstations and is now also available for the PC

2. Other simulators

From a manufacturer's point of view, releasing a PSICE model of their component has some risks. Competitors may be able to work out confidential circuit implementations from the netlist. IBIS, or the "Input/Output Buffer Information Specification," is a device modeling standard that was developed in 1993 by a consortium of companies from within the electronic design industry. IBIS allows the development of device models that preserve the proprietary nature of IC chip designs, while at the same time providing information-rich models for signal integrity and EMC analysis.

IBIS models do not model the functionality of the device as SPICE models do. They simply model how the inputs and outputs switch, their inductance, capacitance, and voltage and current characteristics. However, this has the advantage that models can be created for devices that it would be completely impractical to develop a SPICE model for - for example, the AMD K6 microprocessor!

Although IBIS models will not work directly in a SPICE simulation, there is a tool available for translating IBIS models into SPICE models. It is available here along with installation instructions.

3. Where can I get it?

Demonstration versions of the SPICE simulator are available for download on the web (if you can wait!) at a few locations, some of which are listed below:

MicroSim DesignLab Release 8

Orcad Student Edition Release 9.1


Proteus Lite
This package has a registered and unregistered version, and includes a full schematic capture and PCB layout program as well as a mixed-signal SPICE-based simulator.

Circuit Maker
This program has a full and a student edition. The student edition is available for free download, and comes with a very large library of models.

There are many more listed on Terry Pinnell's site here:

This is a simulator provided free by Linear Technology. It has no node limitations so you can simulate large circuits with it. This is the simulator that I use by choice.

3.1. Demonstration version limitations

The demonstration versions are generally limited to the number of nodes on the circuit they can simulate, and the number of models that come with it. A typical node limit is 60 nodes. This actually represents quite a large circuit. However, once you pop an opamp or two on there (which may have 20 or 30 internal nodes), then you can soon run out.

The solution to this problem is to simulate your circuit in sections. For example, in the RxDetector circuit on this site, I first simulated the linear ramp (the current source charging the capacitor), then when I knew that was working, I replaced it with a Piece-Wise-Linear (PWL) voltage source component in the SPICE library which I set up to create the same linear ramp. Then I simulated the sample and hold amplifier driven by the PWL voltage source.

When splitting your circuit like this, be sure to appreciate the loading of the following section on the previous section. For example, if the SAH had an input current of 10mA (it doesn't thankfully!) then this would affect the linear ramp generator requiring an opamp buffer between the two. The input current of a stage can be measured by placing a simulated current probe at the input, and the affect on the previous section can be simulated using either a resistor load to ground or a current source component on the output of the section.

Other solutions to the problem can be achieved by using simpler device models. For example, if you know that your opamp unity gain buffer signals will never go anywhere neat the supply rails, and the frequency is nowhere near the opamp's limit, you can replace the opamp buffer with a circuit comprising a 1M input resistor between the + and - terminals, and a voltage-dependant-voltage-source component with unity gain at the output, say feeding through an output resistance of 20 Ohms or so. This will reasonably model the opamp configuration, and only requires 1 node whereas the opamp model may have 30 nodes:


4. SPICE models

Most semiconductor manufacturers supply SPICE models of many of their devices, generally the simpler ones like Opamps, comparators, and discrete transistors. There are also third party models available.

I have added a large page (500k) of device model links that I have found on the web. Click here to see it.


A single device SPICE model consists of an ASCII XXX.MOD file. If the device is one of the standard SPICE parts such as diodes, transistors, resistors, capacitors, etc, then it will be represented as a ".model" statement. If it is a more complicated device, then it is represented by several of the standard parts made up into a sub-circuit, and written as a ".subckt" block statement.

Often, several device models are combined into an ASCII library file (XXX.LIB), which is simply the .MOD files concatenated. The library will often be a single manufacturer's devices, or a sub-range of that manufacturer. For example, the very large LTC.LIB file is the whole range of Linear Technology, whereas MOTOR_RF.LIB is Motorola's RF transistor library. The Orcad demonstration package includes several libraries for circuit layout, but only the EVAL.LIB has SPICE models as well. This library includes a range of common analogue and digital devices. You may import models into this library if you like, or just add other libraries complete to the package. If you still want to do circuit layout with the devices you will also need a .OLB library for those parts though (which may be available at

4.1. SPICE component models used in the circuits

This section includes SPICE model files for all the ICs used in the circuits on this site. Your simulator may well already have the basic ones, but several are more obscure. Clicking on the component name will allow you to save the .MOD file to disk.




SPICE model


2N5460 P channel FET




ZVN3306A signal level N channel MOSFET




ZVP3306A signal level P channel MOSFET



Exar and Intersil

ICL8038 signal generator




ICL7660 voltage converter



National Semiconductor

LM324 quad opamp (dual is LM358)



National Semiconductor

LM340T-5.0 5V voltage regulator



National Semiconductor

LM3504 signal generator



National Semiconductor

LM358 dual opamp (quad is LM324)



National Semiconductor

LM385-ADJ voltage reference



National Semiconductor

LM6132A low voltage rail-to-rail opamp




MAX038 signal generator



Vishay-Roederstein MKP1837 1% polypropylene capacitor



SGS Thomson SG1524 PWM generator for SMPS



SGS Thomson

TD340 Full H-bridge controller



Texas Instruments

TL071, TL072, TL074 low noise opamps



4.2. Other SPICE models

Semiconductor manufacturers’ SPICE model sites. Some of the links take you to the SPICE model page. Others you have to search for the device, and then there is a link to the spice model.

Manufacturer and link to models page

Components models supplied

Advanced Linear Devices


Allegro Microsystems

Power ICs

Analog Devices

Opamps, ADCs, DACs

Apex Microtechnology

Power Op-amps


Opamps and other linear devices.




Buffers, Op-amps (BJTs, FET), Op-amp (CMOS)


Op-amps, Buffer Amp., Line Driver, Fet Buffer, Closed Loop Buffer, Current mode Multiplier, Video Amp, Current Amp., Fast Buffer Amp., PNP/NPN Models


Discrete BJT's MOSFET's and JFET's


Hall effect devices

General Semiconductor

Diodes, MOSFET's, BJT's

Harris (Intersil)

Transistor arrays, Opamps






Digital logic and specialised RAMs

Infineon Technologies AG

Mosfets, Diodes, IGBTs, MOVs, Inductors

International Rectifier

Power Mosfets, Rectifiers, IGBTs, Hexfreds, Schottky diodes

Linear Technology

Op-amps, Instrumentation Amps


Op-amps, Buffers, Op-amps (BJTs, FET), Op-amp (CMOS)


RF and microwave diodes



National Semiconductor

Opamps, buffers

Newport Components

DC to DC converters and inductors

On Semiconductor (Motorola)

Opamps, IGBT's MOSFET's BJT's and more


Discrete components




RF Power Mosfets

Shindengen Semiconductor

Diodes and Diode Bridges


Opamps and timers


SCRs, Triacs, Sidactors

Texas Instruments

Op-amps, Comparators, Voltage References

Vishay Siliconix

Power MOSFET's

Zetex Semiconductors

BJTs, Power BJTs, Darlington BJTs, Diodes, Power Mosfets

5. Links

5.1. Links to SPICE model sites

The model search facility

Prentice Hall:
Prentice Hall parts library

If you really need a SPICE model and are prepared to pay for one, try here:

A variety of models of various analogue components including discrete transistors, opamps, and voltage references:

Intusoft supplies some free model libraries:

A links page of online SPICE resources:

Microcap supply a SPICE simulator and have some models on their site:

5.2. Other SPICE and IBIS Links

The website

The EE Compendium SPICE page

An online course in circuit simulation

A Spice page with links for downloading SPICE and manuals:

An online tutorial in using Microsim DesignLab:

SPICE Online users guide:

The SPICE club! Includes a database of models

Links to manufacturer's IBIS models:


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