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Hello Circuits Educators,

As you may know Multisim Touch for iPad was released June 9 on iTunes. If you haven’t heard Multisim Touch for iPad is the newest edition to the Multisim lineup that provides engineers, educators and students a platform to design and simulate analog circuits anywhere. This circuit design app allows users to quickly build circuits with a library of common devices and visualize the performance in an interactive graphical environment. Over the past few weeks we’ve had a good response with many positive comments worldwide.

  Touch Circuits.jpgToday I wanted to share some additional resources for getting started as well as some interesting courseware. This location is the starting point for all things Multisim mobile. If you scroll down the page to the Technical Resources section there are many videos and circuit examples for use with Multisim Touch for iPad. For example, the Getting Started videos cover the basics from building a design to simulating and analyzing a circuit. You can download the Getting Started Circuits directly to the iPad and begin simulating right away.

Multisim Touch for iPad is part of the NI Circuits Teaching Solution which provides an integrated environment for simulation and circuit design across tablets, desktops and teaching hardware. The Multisim Touch Courseware Examples section of the Technical Resources page contains over 30 circuits for first and second year analog circuits courses. These circuits are based on existing Multisim courseware and provide a great starting point for creating, simulating and analyzing circuits on Multisim Touch.

Please let me know if you have any feedback or questions on this or other Multisim topics, or on how you plan to use Multisim Touch in your classroom.

Campbell B

National Instruments


Hello Circuit Designers,

Just a quick note today to let everyone know that Multisim 13.0.1 was released a few months ago in March 2014. This upgrade is available for users with an up-to-date Standard Service Program membership. This release contains improved support for Windows 8 and other minor fixes for Multisim and Ultiboard.

The most noteworthy item is the addition of almost 2,400 new components from 11 different manufacturers. National Instruments has been working closely with the manufacturers listed below to include additional and updated components and simulation models from a broad range of application areas.

ManufacturerNew Components
Analog Devices48
Avago Technologies207
Efficient Power Conversion13
NXP Semiconductors193
ON Semiconductor166
Texas Instruments507

For example, from Vishay and Avago we have added Optocouplers, from Texas Instruments, Infineon, NXP Semiconductors and ON Semiconductor there are almost 500 power MOSFET models. For a complete list of all Multisim Components and Models go here.

Please let me know if you have any feedback or questions on this or any other Multisim topics.

Campbell B

National Instruments


Hello Circuit Designers,

Circuit parameters are a powerful feature introduced in Multisim 13.0 that allows you to have increased flexibility when simulating a circuit. Basically, circuit parameters are user-defined variables that you use to assign a custom value to a component value.

Getting Started with Circuit Parameters:

Using the RLC circuit from the examples included with Multisim (attached to this post), we see that the values of each of the RLC components in the three stages are R=0.5 ohm, L=100nH and C=1nF as defined by the circuit parameters.

Circuit Parameters.jpg

To set a circuit parameter, choose View->Circuit Parameters from the menu. The circuit parameters spreadsheet opens at the bottom of the workspace. From here you can add or edit all circuit parameters. To use a circuit parameter in your design, simply enter the parameter in the value field of a component. As shown below the selected resistor has a value that is twice the value set for R. You can find a good introduction to circuit parameters here.

Resistor Properties.jpg

Circuit parameters provide a powerful option when simulating designs by allowing you to quickly change a number of component values all at once or deduce component values based on design performance specifications. For more complex simulation scenarios you can create case structures to automatically obtain results from multiple simulation runs. Circuit parameters can also be used with sources such as a Pulse Voltage source, for example, by setting a Rise Time = .001 * period, a Pulse width = .5 * period and then iterate over multiple values of the period.

Here is a more advanced design that demonstrates a powerful way of evaluating different design cases and tuning multiple parameters of the circuit at the same time. The goal is to figure what component values will help meeting the design specifications.

Please let me know if you have any feedback or questions on this or any other Multisim topics.

Campbell B

National Instruments


Hello Circuit Designers,

I wanted to let everyone know that Multisim Touch for iPad is now available on iTunes. The newest addition to the Multisim lineup provides engineers, educators and students a platform to design and simulate analog circuits anywhere. This low-cost, native SPICE simulation and design app allows users to quickly build circuits with a library of common devices and visualize performance in an interactive graphical environment.

Multisim Scematic_Capture for iPad ss.jpg

Building a circuit is simply a matter of tapping components from the component bins and dragging on to the workspace. Tap a terminal to begin a wire and the tap a destination to complete the connection. Multisim Touch supports rotate components, voltage and current probes, set component values, undo/redo and many other standard features of the full Multisim desktop versions. These Multisim Touch Getting Started Videos give a good introduction to creating and simulating a design.

To share and store circuit files Multisim Touch provides integration with email and DropboxTM. A design on the tablet can be shared with other Multisim Touch users. If the design is ready to be integrated into a more sophisticated project it can also be opened in Multisim for the desktop. Circuit designers can then take advantage of the advanced technology of Multisim on the desktop including more analyses, more components as well as integration to PCB layout (Ultiboard) or connection to NI hardware such as NI myDAQ, NI ELVIS and LabVIEW.

Please let me know if you have any feedback or questions on this or any other Multisim topics.

Campbell B

National Instruments


When creating systems that include NI DAQ, NI Single-Board RIO, NI CompactRIO, or other hardware, circuit designers often need to develop signal conditioning boards, test fixtures, and other circuitry that are not available directly off the shelf. Multisim provides a large database of predefined, pin-accurate connector symbols that save hours when developing accessories for these hardware platforms. Rather than having to create a custom 50+ pin symbols and footprints, there is already a pre-populated library of such devices.

In Multisim 13.0 design templates has been added to accelerate prototype development and enable design reuse. The user defined templates for circuit schematics and PCB layouts help the user save a significant amount of time on the design they work on repeatedly with preconfigured devices, part placement, routing and board outlines.


Here is a list of the available NI hardware templates. Each of the templates include:

  1. A schematic file with a brief description, all the connector symbols, and the recommended grounding and power supply schemes.
  2. A PCB layout file with the recommended board dimensions, accurate holes for standoffs, and accurate placement of mating connectors.

NI Single Board RIO 9623/9626
NI Single Board RIO 9605/9606
NI Single Board RIO GPIC 9683
NI myRIO Board Only Single MXP
NI myRIO Board Only Dual MXP
NI myRIO Enclosed only
NI 68-pin Connector to R-Series DAQ
NI 68-pin Connector to M-Series DAQ

Additional Resources:


Watch this new webcast on the collaboration between NI and Microchip to provide a holistic approach to electronic circuits design, research , and education with Multisim and cutting-edge simulation models and components

To download a free evaluation of the latest edition of Multisim Professional, click here

Visit, or learn more at



A fuse is a temperature sensitive device that plays a critical role in circuit protection. Since the operating temperature has an effect on fuse performance and lifetime, it is extremely valuable to be able to model fuse thermal derating in a SPICE environment while the operating temperature should be taken into consideration when selecting the fuse current rating.

This new model implements a very fast acting fuse that includes its thermal derating curve. Simulation will show how the operating current and temperature have an effect on the fuse’s performance and lifetime.

Fuse Model with Thermal Derating Parameters

The Multisim model is developed based on the approach introduced in this paper and is shown in Fig. 1. The implemented fuse model is for the 0603SFV050F/32-2 very fast-Acting chip fuses by TE Connectivity. The parameters used inside the models are as follows:

  • the rated current: irs=0.5A
  • the nominal cold DCR: RFref=0.860Ω
  • the nominal I2t: I2tref=0.0093A2sec

The model requires the fuse resistance at the end of the pre-arcing time, rfm, which is usually provided in the datasheet. This resistance can be determined through laboratory measurements. Another variant to determine the rfm is to consider that the heating process of the fuse is rapid and adiabatic. Knowing the fuse material, the fuse resistance at room temperature, RF, using equation (1), rfm can be calculated considering that the resistance versus temperature is linear:


where α is the temperature coefficient of the fuse material, Tm is the melting temperature of the fusing material, and T0 is the reference temperature. The length and section area of the fuse are considered constant.

The thermal derating curve is implemented using a lookup table, while the values above were taken from the fuse manufacturer datasheet. The variation of the fuse resistance with temperature and also the variation of the I2t in percent with temperature are all taken into account inside the model.


Figure 1. Fuse SPICE model internal structure

Note that in the model above the W2 current controlled switch is used for removing the path for Cfuse discharge after the fuse is blown. To view the model of the fuse double click on it and then click on the Edit Model button under the Value tab.

Running the Fuse Model

The fuse is placed in a simple test circuit (attached to the article) to verify its operation in an interactive simulation setup.


Figure 2. Test circuit setup


Figure 3. Load voltage during when over current passes through the fuse

The Parameter Sweep Analyses can be used, to show the fuse’s response at different currents. In the Analysis Sweep field, the Transient Analysis option must be chosen. Both the Transient and Parameter Sweep Analyses configurations are shown below in Figure 4.




Figure 4. Analysis setup in Multisim

Running this sweep analysis, the transient response of the fast acting sweep can be evaluated under different current conditions. This is valuable in determining how fast the fuse will melt and how much energy is needed to do so. The results are shown in Figure 5.


Figure 5. Analysis results in Multisim

Moreover, the effect of the ambient temperature could be analyzed in Multisim. It is important to understand how differently the fuse will behave at 75 degrees from a normal 25 degrees room temperature. For this purpose a temperature sweep from 25 to 125 degrees is setup in Multisim to run the same circuit under a constant load current.


Figure 6. Temperature sweep setup in Multisim


Figure 7. Simulation results of the temperature sweep

The ismulation results show that the higher the environment temperature is the faster the switch will respond to the over-current.

You can download this advanced fuse model and start using it in the attachment.

Clcik here to download a 45-day free evaluation of the latest release of Multisim.


NI Multisim is a powerful tool used to simulate and prototype power electronics circuit designs. Multisim has large database of configurable power component models along with existing SPICE models from various semiconductor manufacturers. The simulation capabilities in Multisim enable the evaluation of different power circuits of different ratings at an early design stage.

This is the first of a series of blog posts about new power electronics models specifically developed for simulations renewable energy applications in NI Multisim. The models were developed in collaboration with the Virtual Instrumentation and Renewable Energy Laboratory at the Transilvania University of Brasov in Romania.

In this article, three solar Photo-Voltaic (PV) cell models are presented:

1. Basic PV Cell

this model represents the ideal and most simplistic case of a PV cell model. the solar cell is modeled using an ideal current source in parallel with a diode and a load resistance.


The model is available in the Multisim file Testing the Solar Cell Modules_1.ms13 attached to this post. Connected to the model are two DC sources; Virrad representing the level of illumination where 1000V=1000W/m2 a, while Vbias allows the variation of the bias point to measure the output I-V characteristics. In a real world application, Vbias would be replaced by a load.


The internal parameters of the models are set based on a Si solar cell example:

  • The reverse saturation current (Io = 10-11 A)
  • The short circuit current (Isc = 0.034 A)
  • The area of the solar cell (A = 1cm2)

These parameters could be viewed and altered simply by double-clicking the component on the schematic and clicking on Edit model in the Value tab:


Running a DC Sweep simulation in Multisim to evaluate the output current at different bias points as well as the output power, the below graph could be reproduced



2. Advanced PV Cell with Series and Shunt Resistance

This model is based on the single exponential model published in [1]. It add a shunt and series parameters to model the panel resistance.


The same Si solar cell example was used to set the following parameters:

  • The constant material (B = 5.769*106 )
  • The short circuit current (Isc = 0.034 A)
  • The area of the solar cell (A = 1cm2)
  • The energy bangap (Eg = 1.11eV)
  • The series resistance (Rs = 0.1 Ω)
  • The shunt resistance (Rsh = 10000 Ω)

In this advanced model the open circuit voltage of the solar cell depends on the material of the solar cell expressed in the material constant B and the energy band gap Eg. The material constant can be determined using the variation of the reverse saturation current function of the temperature and it theoretically derives from this relation:


While the values of the energy Bandgap for some important semiconductor materials are available in the table below:

Semiconductor materials

Energy bangap [eV]












The model and the test circuit are available in the attachment Testing the Solar Cell Modules_2.ms13. Running a Nested DC Sweep yields the following I-V characteristics of the PV cell



3. Advanced PV Panel

This is a model of a PV panel based on a number of individual solar cells connected in series using one diode model with irradiance and temperature parameters. It is based on the physical parameters of the BP-MSX120 PV panel, however these parameters could be altered in the model to match other PV panels:

  • The short circuit current (Isc = 3.87 A)
  • The series resistance (Rs = 0.47 Ω)
  • The shunt resistance (Rsh = 1365 Ω)
  • The temperature coefficient of the power (kp = −0.5 ± 0. 05)
  • The number of solar cells in series (ns = 72)
  • The ideality factor of diode (A = 1.397)

The example testing circuit to validate this model is in the attached file Testing the Solar Cell Modules_3.ms13

A nested temperature sweep is performed to evaluate the I-V characteristics of the panel under different temperature conditions:



About the Virtual Instrumentation and Renewable Energy Laboratory - Transilvania University

Laboratory members:

            Dr. Petru Adrian COTFAS

            Dr. Daniel Tudor COTFAS

The lab is integrated in the Electronics and Computers Department, Electronics and Computers Science Faculty, Transilvania University of Brasov. Transilvania University of Brasov was founded in 1948 and has now 18 faculties, offering bachelor, master and doctoral studies to over 22000 students. Advanced research is developed in 22 centers focusing on major topics of sustainable development: Renewable Energy Systems, novel Energy Efficiency in processes, advanced solutions for Energy Saving products and processes, Natural Resources preservation and use, Health and Life Quality, and Education, Culture, Communication and Economic Development.

There are many educational and industrial applications using the NI products at the University:

  • Simulation of Physics labs using the graphical programming language LabVIEW 
  • SolarLab – educational and research system powered by NI LabVIEW and NI ELVIS II platform



  • RELab (Renewable Energy Laboratory) – educational and research system powered by NI LabVIEW and NI ELVIS II and myDAQ platforms


  • STNV 25120469 – research contract for development of drivers LabVIEW Ecochemie - Netherlands
  • Weighing and monitoring system of Mass Distribution for S.C. IAR S.A. Brasov, Romania
  • Management system for the utilities implemented at S.C. IAR S.A. Brasov, Romania

The ReLab system is a very good solution for the study of the renewable energy. The design of the entire RELab circuit was done using the NI Multism and NI Ultiboard. The RELab system was recognized as a break-through tool in education and won three awards at international competitions organized by National Instruments:

  • Graphical System Design Achievement Awards - Education category - August 2013
  • Graphical System Design Achievement Awards - Editors Choice Award - August 2013
  • Graphical System Design Achievement Awards - NI Community’s Choice - August 2013.


  1. 1.   D. T. Cotfas, P. A. Cotfas, S. Kaplanis: Methods to determine the dc parameters of solar cells: A critical review, Renewable and Sustainable Energy Reviews, vol. 28, 2013, pp. 588–596.
  2. 2.
  3. 3.   D. Sera, R. Teodorescu, PV panel model based on datasheet values, Industrial Electronics, 2007. ISIE 2007. IEEE International Symposium on, pp. 2392 – 2396, 2007

Download All

Creating simulatable components in Multisim 13.0 is easier than ever thanks to the enhancements to the Component Wizard. Specifically, the Component Wizard now checks the SPICE code of imported models, displays error messages and, my favorite improvement, features an intuitive way to configure the mapping information between symbol and model, which is a critical step in the component creation process. Let’s explore this feature.

For this example I will be using a SPICE model for the AD743  opamp, which was downloaded from the Analog Devices website. After entering the symbol information and model data, the Component Wizard will ask for the symbol to model mapping; this information can be found in the SPICE model, as shown below:

* Node assignments

*             non-inverting input

*             | inverting input

*             | |  positive supply

*             | |  |  negative supply

*             | |  |  |  output

*             | |  |  |  |

.SUBCKT AD743 1 2 99 50 37




IOS 1 2 DC 12.5E-12

CIN 1 2 20E-12

EOS 9 3 POLY(1) 16 31 100E-6 1

In Multisim 12 (and previous versions), the model nodes in the pin mapping table were selected by order (1, 2, 3, 4, 5), not by the name (1, 2, 99, 50, 37) they have in the SPICE model. This means users needed to open the SPICE model, locate the node names, and manually map them by order. The use of a table was recommended to make sure the mapping was accurate:


Here is screenshot of the pin mapping table in Multisim 12:


If  the pin mapping table is incorrect, your custom component will not work, Multisim will display errors in the netlist or the simulation will output incorrect values.

In Multisim 13.0 we made things easier for you. Take a look of the following image:


Do you see the difference? Not only we have a display of the symbol and the model, but also the pin mapping table recognizes the node names. This means that you no longer have to open the SPICE model and manually map node name to node position; what you see in the SPICE model is what you get in the pin mapping table.

I’m sure this improvement will save you time and eliminate errors.

All the best,

Fernando Dominguez



Attend NIDays and join thousands of industry experts and NI employees worldwide to learn about the latest technologies and trends in design, test, and control. Hear about recent software upgrades including NI Multisim and NI LabVIEW, emerging hardware platforms, and industry applications. Learn how you can improve performance, and find out how solutions-based on NI products can save you time and money without sacrificing flexibility and longevity.

Multisim will be present with a booth and new demos.

Join us TODAY at the NIDays event in Washington DC

Future NIDays events in North America:



NI is happy to announce that Multisim 13.0 is now available. The R&D focus for Multisim for industrial/professional use is to add powerful design capabilities for analog and mixed-mode simulation, improve design validation, and enable rapid and accurate PCB prototyping.

Feature Highlights of Multisim 13.0 (Download the attached presentation to learn more)

Enhanced Circuit Simulation with Circuit Parameters and NI Multisim API Toolkit

User defined circuit parameters in Multisim 13.0 enable engineers to easily calculate, change and sweep critical component parameters in advanced analog and power application designs. In conjunction with parameter sweep, engineers can modify and iterate parametric information to achieve optimal values for their components/devices to better understand circuit behavior under varying conditions and performance metrics.

The NI Multisim API Toolkit is a standardization of a widely used tool that enables engineers to automate simulation analyses from the NI LabVIEW environment. This unique feature (only available in NI Multisim) allows customers to extend simulation to the graphical design environment of NI LabVIEW to define countless applications, acquire and correlate measurements, as well as define domain specific analyses that are not possible with conventional simulation environments..

Accurate Simulation with 26,000+ Devices from Leading Semiconductor Manufacturers

Multisim expands upon a vast library with more devices that enable accurate design and analysis of circuit design. Included in this release is a customizable diode, IGBT, and MOSFET components with thermal behavior information for power electronics analysis.

Multisim 13.0 also brings over 26,000 components that are verified and validated by leading semiconductor manufacturers enabling accurate circuit evaluation on the desktop:


New Components / Updates

Analog Devices

100+ new amplifier components for instrumentation, differential, current sense, audio, and special functions


500+ new and updated discrete BJT, diode, and zener components


eGAN MOSFET components for  efficient power application design

ON Semiconductor

400+ new discrete components


500+ new thermal MOSFET components and 100+ new microcontroller ICs


1300+ new components such as amplifiers and regulators

Test Mating Connectors

Updated symbol/footprint libraries from leading manufacturers such as Phoenix for developing custom accessories for test fixtures

Accelerated PCB Prototyping and Design Reuse

User configurable templates will help engineers to create, share and modify design templates that take into consideration critical devices, spacing, layout consideration and settings.  With ready-to-use daughterboard and test fixture templates for hardware such as NI myRIO, NI sbRIO, NI ELVIS, NI CompactRIO, NI myDAQ as well as platforms from Digilent or generic hardware, engineers can improve time-to-prototype.

Also included in Multisim 13.0 are numerous updates to critical features in prototyping such as multi-section components to ensure the integrity of device naming, quicker device updating/editing as well as an improved user interface.

Best Regards,

Mahmoud W

National Instruments



NI Multisim is equipping engineers and researchers with design tools improving their approach of electronic circuits design. Multisim is also widely used at leading aerospace companies world-wide, government research institutions, national laboratories, and mil/aero consulting organizations.

With best-in-class analog and mixed-mode circuit design capabilities, as well as integrated PCB design tools, Multisim has proven success in a wide range of applications from avionics equipment for data acquisition and imaging, to communication applications complementing RF systems, to the design of defense electronics equipment.

Watch this on-demand webinar and learn more about Multisim circuit simulation and PCB design of Aero...


Instrumentation Amplifiers (InAmps) play a vital role in low-frequency data acquisition applications. Low-voltage signals in noisy environments require pre-amplifiers that exhibit very high Common Mode Rejection Ratio (CMRR), high input impedance, low output impedance, and excellent noise performance. In some cases, such as in defense electronics, gain drift is a critical parameter to guarantee the system behaves as expected at higher temperatures.

InAmps are a viable choice to meet all these design specifications in the test and measurement world. This is why semiconductor manufacturers have been increasing their portfolio of monolithic InAmp chips. Board designers with such components could save time to meet their design specifications, although in some cases the customization of discrete amplifiers is still needed.

At NI, we work with semiconductor manufacturers to equip Multisim’s library with a large selection of InAmps models and footprint. All these models are provided by leading manufacturers and validated by NI R&D engineers guaranteeing accurate simulation results in Multisim.

AMP01 Aerospace Instrumentation Amplifier from Analog Devices

This is a monolithic instrumentation amplifier by Analog Devices designed for high-precision data acquisition and instrumentation applications. It shows a combination of performance attributes that take the instrumentation amplifier one step further towards the ideal amplifier, datasheet here.

The figure below shows a typical InAmp configuration for driving a 50 Ω loads from the part’s datasheet.


Simulation as a High Performance Non-inverting Operational Amplifier in Multisim

This instrumentation amplifier could also be configured as a high performance operational amplifier. In many applications, this configuration could be a replacement of amplifier-buffer combinations. Some of the advantages of InAmps in such configuration are the low harmonic distortion, improved gain offset drift, and excellent linearity.

This configuration is built in Multisim and performance attributes are analyzed using the simulation and analysis tools in the design environment.


Instrumentation amplifier configuration as a differential amplifier. Drag and drop PNG image into Multisim to load the circuit.


Transient time response of amplifier operation. Output is 2Vp-p


Fourier analysis and a THD of 0.00014%

Download Multisim free evaluation


Hello Circuit Designers,

NI Multisim includes many circuit simulation tools (all available under Simulate>Analyses in the Multisim menu). One of the most critical pramaters affecting a circuit's behavior is the noise.

Using Multisim noise analysis, designers can accurately simulate the effects of noise and accordingly make the right design decisions. Resistor thermal noise could be evaluated as well as also other noise effects caused by semiconductor components such as shot noise, flicker noise, and 1/f noise.

For a step-by-step tutorial on how to properly setup noise analysis in Multisim, refer to this page. What I will be highlighting in the rest of this post is a practical design use-case where noise analysis is beneficial.

Design Use-Case

Assume there is a slowly-varying (<5Hz) input signal with a voltage range of 60mV which needs to be amplified and digitized. The requirement is to determine whether or not the circuit shown below, in combination with a 16-bit A/D, achieves a Signal-to-Noise (SNR) ratio of 100dB after the amplified signal is digitized. If it does not achieve this specification, then a noise filter should be added such that it does.


With the amplifier gain of 100, the output signal has a range of 6V. The RMS voltage noise, Vn_Totalrms , corresponding to 100dB and that which must not be exceeded at the A/D input is calculated as follows:

Of course, the A/D itself has quantization noise. The quantization noise on a 16-bit A/D operating with the same +5V/-5V supplies is:

Since the A/D quantization noise and the noise from the amplifier circuit, Vn_Amprms, are uncorrelated, they add up as a sum of squares, namely:

Therefore, the maximum RMS voltage noise produced by the Amplification circuit is 41 uVrms.

At this point, we can use Multisim to determine the noise that this amplifer circuit produces on node Out and see if it is less than 41uV. There are few ways to do this. We can use the Calculate total noise values option in the Noise Analysis dialog. This would provide a scalar value representing the integrated noise across a specified bandwidth. However this information would not provide to us a good indication of how integrated noise is affected by bandwidth, in case we need to make adjustments to the circuit. Therefore, we shall use the Calculate power spectral density curves option and then use some post processing functions to get a better understanding of how noise is affected by bandwidth.

In the Analysis tab, let's use the following settings:


In the Frequency parameters tab, let's use the following settings:


The analysis is carried out across a very large bandwidth (0.1Hz to 10GHz) so that we have an entire picture of how the noise varies with frequency. The simulation will be a plot of noise density in units V2/Hz. However, we are looking for an integrated noise plot in units Vrms. To do this, we can create an expression using the integral() function. It will return a plot in units V2, so we simply apply the sqrt() function to get the desired result. The overall expression is sqrt(integral(onoise_spectrum)). The result is shown below.


The shapes of the curves match intuition. The noise density plot is high at very low frequencies as a result of the op-amp’s 1/f noise. At approximately the cut-off frequency of the circuit, the noise density starts to fall, as would all signals in the circuit. The Integrated Noise plot represents the running integral (starting at 1Hz) of the noise density plot. Obviously starting with zero noise for zero bandwidth, the integrated noise climbs quickly, leveling off shortly after the cut-off frequency when little noise is being contributed by each frequency.

Therefore, if no additional filtering is added to the circuit to limit its bandwidth, the Integrated Noise plot shows that there will be approximately 530uV of noise on the output – far above our of required limit 41uV. However the plot shows us that in order to limit the noise to 41uV, the bandwidth should be limited to approximately 335Hz. So let us add-in a simple, buffered R-C filter as follows:


Also note that adding the buffer and resistors would introduce noise which are picked up at “out” pin.

The above circuit produces the following noise curves:


Now, the Integrated Noise has leveled off at approximately 53uV – a lot closer to the required 41uV!  Therefore we may want to limit the bandwidth slightly more and see how that takes effect in the Multisim simulation. The purpose of this example was to illustrate how NI Multisim’s Noise Analysis can be such a beneficial tool for the designer.


Hello Circuit Designers,

I wanted to highlight some add-on tools that enable a high-level simulation of Analog to Digital Converters (ADC) in the Multisim SPICE environment.

ADCs are used everywhere where an analog signal needs to be processed in the digital domain, such as audio/video applications, control and monitoring, software defined radio, instrumentation, and many other. Simulating an analog front-end in Multisim is valuable to optimize the signal conditionning circuitry before building a prototype, however, it is also important to learn how these signals will look like in the digital domain and perform different measurements on them.

The ADC add-ons are behavioral models developed in NI LabVIEW and compiled to be used within Multisim. Among 70 other tools, they are available for download at the Multisim custom instruments and analyses community. For these specific instruments, make sure you have the LabVIEW Run-Time Engine 2010 installed, and follow the setup instructions here.

The models mainly focus on the modeling of the front-end of the ADC parameters (such as the capacitive input impedance), yet not involving some of the complex calculations at the digital back-end of the ADC (such as I2C transformation).

Here are some screenshots from the ADC measurement instrument.

Multisim Schematic:


Input and digitized analog signal output, ADC configuration and frequency response are shown at the bottom:


Windowed analog signal and modeling of the ADC input impedance (note also the dynamic input range):


Output digital word and the transfer function measurements after adding some signal imparements:


Non-linearity measurements at the bottom:



Hello Circuit Designers,

I would like to share with you a new proof of concept design that takes advantage of multiple NI tools. The design is a Low Noise Amplifier (LNA) operating at 10 GHz fully analyzed in AWR's Microwave Office. Along with the LNA, a peripheral low-frequency circuit providing the needed bias levels for the FET is simulated in NI Multisim. Finally, the LNA is imported into Multisim as a footprint only component to be combined with the bias circuit. A final PCB prototype of the complete system is created using NI Ultiboard.


Read the detailed tutorial here

1. Evaluation of the 10 GHz LNA performance in MWO

This design of a 10 GHz LNA built on 10 mil alumina is using a NEC 76038 GaAs MESFET.  Running the analysis of the circuit, you learn that the LNA has 7.7dB gain and 2.15dB NF at 10 GHz.

Designing this amplifier in MWO you can take advantages of the real-time tuning, frequency subset Smith Chart plots of noise and matching circles, and the X-Models for discontinuities accuracy to validate the performance of the amplifier.


2. Creation of a LNA footprint component to use in Multisim

This step means to export the layout of this LNA in a DXF format and integrate it into Multisim as a new component. Check the step-by-step tutorial to learn more

3. Design of low frequency bias network in Multisim

The next step in this example is to accurately validate the circuit performance of a biasing circuit that takes a 12VDC input and outputs 2 arbitrary voltage levels for Gate and Drain biasing of the MESFET at -0.7V and 5V respectively. Eventually this bias circuit will be integrated with the LNA on a single PCB.


4. Prototyping the complete system in Ultiboard

Finally, the LNA component is added to the Multisim design and a final PCB layout is created using Ultiboard.




Let me know if you have ideas for similar use-cases.

Mahmoud W

National Instruments


Hello Circuit Designers,

National Instruments is excited to be back in Santa Clara CA for this year's DesignCon. Come and join us at booth 707 and check the most recent updates of NI products presented by our design and test experts.

NI's Business and Technology Fellow, Mike Santori, will be giving a keynote speech on software-designed instrumentation. Also, four technical papers are presented by NI engineers throughout the conference (details here).

Last by not least, the NI Multisim team will be present with great demos on the most recent applications in SPICE simulation, PCB layout, and system design with LabVIEW FPGA.

See you all on Jan 29th.

Mahmoud W

National Instruments



Hello Circuit Designers,

In power electronics design, the thermal behavior of switching elements is critical to evaluate the performance of a Switched Mode Power Supply (SMPS).

Thermal behavior means the performance of the semiconductor switching element as the conducting p-n junction heats up.

In the most recent update release of Multisim, over 500 new MOSFET models from Infineon Technologies have been added to Multisim's library of components. Many of these models include the SPICE thermal models.

SPICE thermal modeling is an interesting topic that will be discussing in a future post. For now, let's go over the different levels (types) of thermal modeling of the Infineon MOSFETs in Multisim.

Level 1 Models: Fixed Junction Temperature during the Simulation

The circuit below is a simple buck converter stepping down a 10V input to a 5V output. In Level 1 models, during Transient Analysis, the junction temperature is fixed using the TEMP setting

within the simulator's SPICE options. Alternatively you can run Temperature Sweep Analysis which overrides this setting as it sweeps its value.


Drag and drop .png image into Multisim to load the same circuit

Note that in Multisim, if you go to Simulate>Analyses>Transient Analysis under the Analysis Options tab, select to use custom settings and click on customize to change the parameter TEMP indicating the junction temperature used in any transient simulation (by default it is set to 27 degrees Celsius)

2.png  3.PNG

Select Simulate>Analyses>Temperature Sweep analysis to perform two transient analysis runs - at 27°C and 60°C. This will run until reaching a steady state at both the load voltage and current display.

Note that Level 1 models are not electro-thermal models. If the goal is to predict the junction temperature value, you need to use the Level 3 models.



Level 3 Models: Simulation of Electro-Thermal Models

This example is the same buck converter except that the switching MOSFET is a level 3 model that includes electro-thermal behavior of the junction (i.e heating up of the junction during transient simulaiton). The ambient temperature is modeled using the DC voltage TAmb and the MOSFET case thermal resistance is modeled using RthCA.


Drag and drop .png image into Multisim to load the same circuit

If you run a transient analysis on the circuit, you can see the junction heating up from the ambient temperature (defined in SPICE) of 27 degrees to about 32.4 degrees after 20msec of running the supply.




Hello Circuit Designers,

PCB Libraries offers tools that are intended to eliminate a vast amount of duplication effort and achieve some level of standardization in creation of PCB footprints.  NI Ultiboard is now incorporated within the "PCB Footprint Expert" tool to easily generate IPC standard parts. Having a list of the footprint dimensions in a spreadsheet or from the manufacturer datasheet, you can quickly create that component in Ultiboard using this highly productive tool.

The PCB Expert tool comes in two editions:

  • PCB Expert Lite, a free edition with basic footprint creation functionalities
  • PCB Expert Full, with advanced footprint creations features




The ABM source is a powerful component that allows users to create a voltage or current source based on a mathematical or conditional expression.  For those who are not familiar with SPICE syntax, you can open the attached Multisim file to view the expressions offer in NI Multisim.  You can copy/paste the functions you need and connect them together to create your custom expression.

Creating a component using the ABM expressions allow you to reuse the expression in the same circuit without re-entering and also, it makes the schematic easier to read since the expression inputs are wired together.  To view the model, double-click on a component and then click Edit Model button.  The model consists of three lines; a .suckt statement, the expression and an .ends statement.  By viewing the attached examples, hopefully, you will understand how you can use the ABM expressions to create a complex custom component.

Create a Custom Component Tutorial

The attached Multisim library was created in Multisim 12, if you want to add these parts to your database, select Tools» Database» Merge Database. If you are using newer version, use the database convert option instead.

For more information about the AMB source, refer to the Analog Behaviour Model Source white paper

Download All

LabVIEW instruments are great tools that Multisim users, including myself, often forget about probably because they require one single extra step of installation to get them to work.

I wanted to write down this post as a quick refresher of what the LabVIEW instruments for Multisim are and how they can help in the accurate validation of your circuit design.

What is a LabVIEW instrument?

In simple words, they are additional "nodes or components" placed on your circuit schematic to perform a special functionality that could only be done using LabVIEW blocks. Examples of these functionalities would be the signal generation of a special waveform, a special calculation of your simulation output such as the Total Harmonic Distortion (THD) of an amplified signal, or even a utility functionality such as live connection to the Digi-Key database to get information on parts availability and pricing.


Do I have to be a LabVIEW user to use LabVIEW instruments in Multisim?

No, the LabVIEW instruments are compiled as .llb files that you simply need to copy and paste under the specified directory of the LabVIEW instruments in Multisim. The directory is the one defined under Options>Global Preferences in the Multisim menu under User LabVIEW instruments path


Once you've done so, the imported instruments will appear in  the instruments toolbar in Multisim


How can I create my own LabVIEW instrument for Multisim?

Here is a step-by-step tutorial that explains how to create your own input or output instrument

Where can I find ready-to-use LabVIEW instruments for different functionalities?

There is a community page that includes about 70 instruemnts for a wide range of applications; from advanced signal generation, to complex visualization, application specific analysis and calculation, and many others. Simply go

Can I connect to hardware and import real-world signals into circuit simulation using these instruments?

Definitely! The simplest example would be the microphone and speaker circuit in the Multisim samples folder. In Multisim go to File>Open samples under LabVIEW Instruments and pick the Microphone and Speaker sample design.

In this example you can connect to your computer microphone to pick up an audio signal, stream it as an input signal into Multisim (for filtering, amplification, or mixing), then feeding it back to your computer speaker for play-back.


Let us know ideas of instruments and analyses that you would like to see in Multisim.

Mahmoud W

National Instruments


Hello Circuit Designers,

When creating PCB layouts, many routing aspects that may not be accounted for in the SPICE simulation should be accounted for. One of the most critical routing parameters affecting the quality of the signals on the PCB is impedance matching.

For low-frequency analog signals impedance matching is easy to achieve using simple buffer stages with high input impedance and low output impedance to maximize the power transfer at each stage of the design. However, when the frequency of the analog signal gets to the Mega-Hertz range, the PCB trace itself becomes a transmission line of a distributor nature. In simple words, the trace acts like a chain of series inductors and parallel capacitors. These elements are able to store energy and reflect it back unless the termination is a load resistance equal to the characteristic impedance of that transmission line (calculated by the below equation).2.pngThe same concept applies to all digital signals since they have an infinte span in the frequency domain.


The following two graphs display a 5V digital logic signal propagating through a 50-ohm transmission line. In the first graph the line is open-ended, the second case the line is terminated with a 42-ohm load (close to perfectly matched).



As you can see on the first graph, the reflection on the open-ended line caused a ripple of about 1V on the signal level which could propate back into the circuit and damage it.

To be able to create matched traces and avoid undesired reflections on the PCB, you need to answer these questions:

1. How thick is the PCB and what dielectric material is it made of?

2. What is the impedance of the load? (50 or 75 ohms in most of the cases)

Using these parameters, Ultiboard's transmission line calculator can help you determine the optimum width of the traces you are about to lay down on your board. Simply go to Tools>PCB transmission line calculator in Ultiboard's menu and enter these parameters as shown in the screenshot below.

(Note: choose the type of the transmission line based on where the trace the ground plane are. For example, pick Microstrip if the trace is on the top layer and the ground plane is on the first copper inner layer. In this case the board thickness will be the height (H) between these two layers)

Mahmoud W

National Instruments



Hello circuit designers,

NI Multisim features more than 450 predefined standard connector symbols and footprints to accurately prototype custom circuitry for different hardware platforms.

More than 180 of these connectors are specific to NI hardware systems. A 68-pin VHDCI connector is used to build custom-load boards for single-ended test and measurement applications based on the NI R-series data acquistion modules. These modules use an FPGA-based system timing controller to make all analog and digital I/O configurable for application-specific operation. The connector comes in both vertical (NI-780389) and right-angled (NI-778914) standards, and is used on all the PXI and PCI R-series modules.

Depending on the module you are using, different DIO, AI, and AO allocations are assigned to the connector pins. Multisim simplifies the schematic capture process of these components on your design with dedicated component sections for each functionality.

The screenshots below demonstrate how these components look like in the Multisim database:


Connector placement in Multisim:


Ultiboard footprint and 3D view:

3.png          4.png

Always looking for your feedback.

Happy Thanksgiving!

Mahmoud W


Hello Circuit Designers,

Machine applications require knowledge of a wide range of system components and parameters. The modeling and simulation of these parameters are not easy tasks, at the same time, they remain very critical to the accuracy of the design.

These designs usually involve an analog plant of the power electronics switching components. In addition, to accurately control the switching of IGBTs or MOSFETs, a preliminary controller behavior needs to be simulated. Finally, the load of the system, such as a motor, needs to be modeled based on specific physical parameters.

Below is a sample Multisim design of a DC motor driver with closed loop control showing how you can evaluate all these aspects of the design performance within a single simulation environment.

The design could also be found in the Multisim samples folder under the Machines sub-folder.

The design includes accurate models of the following components:

1. A 3-phase signal generator, modeling the grid input.


2. A 3-phase diode bridge rectifier with parametrizable voltage drops and on/off resistances.


3. An H-bridge network of four transistor-diodes (basic IGBTs)  to drive the motor. Components are also parametrizable to account for electrical behavior.


4. Models of a DC machine and a speed encoder to simulate the load effect based on physical parameters of the motor and to provide an input speed to a closed loop controller.


5. Partial Integral (PI) controller block that reads the speed input and provide control signals to a Pulse Width Modulator (PWM) that drives the switching of the IGBTs.


All these components are provided in the master database of Multisim 12.0 and can be the building blocks of your power electronics system. Parameters such as the transient current through the motor, the speed settling, the control signal levels, and the ripples on the DC link of this system could be evaluated running a transient simulation of the circuit shown below. Simply drag and drop it into your Multisim design sheet.


Entire circuit design in Multisim, drag and drop into your Multisim design environment to load.        


Motor speed settling to 4000 rpm, then getting stepped down to 3500 rpm using the PI closed loop control block in Multisim


Hello Circuit Designers,

Sinking and Sourcing are terms used to define the control of direct current flow in a load. The concept of sourcing and sinking is independent of the component (transistor, mechanical relay) that implements the operation. While this concept applies to any DC circuitry; the component that implements the circuitry may vary.

A typical application of sinking and sourcing digital inputs is in the connectivity of Automotive Engine Control Units (ECU). The NI-9425 and NI-9426 C-Series modules provide such functionalities.

From a design standpoint. Multisim offers the ability to model this behavior based on electric models of the real components. Accounting for signal delays, power dissipation, and voltage and current levels which are all critical parameters to evaluate before deploying the system.

I created the schematic diagram below to illustrate this idea, the switching itself could be implemented in many different ways. Let me know your feedback on this application.

Mahmoud W

National Instruments



It was great seeing you all at PCB West 2012!

We've heard very good feedback about the Multisim booth and NI's presence in the conference. The most exciting news was Multisim winning the New Product Introduction (NPI) award at the show for the new Multisim and LabVIEW co-simulation functionality.

We are looking forward for next year's show. In the mean time, our R&D team is working hard to add more innovative features into our Multisim product.

Mahmoud W

National Instruments




Come and joing us TODAY at the expo floor of PCB West 2012!

NI Multisim is present with demos, news, evaluation station, CDs, and more.

We have updates on:

See you all there,

Mahmoud W

National Instruments


Hello Circuit Designers,

The NI design solution is now enabling engineers around the world to develop a new platform of commercial grid-tied SMPS products such as solar inverters. This solution provides a method to reduce the cost, risk, and development time necessary to bring a ready-to-deploy system to market. All through improvements in platform-based design technologies.

The most recent edition of the Design News magazine featured an article about Solar Inverter design and the NI solution. Check it out here.

An important element of this solution is the co-simulation of Multisim analog plants and LabVIEW FPGA controller code. This approach breaks the domain boundaries between the analog world of power and the digital world of software allowing domain experts to look at the overall design of the system.

To learn more about our solution:




Hello Circuit Designers,

I wanted to bring your attention to recent update!

To be able to run a LabVIEW instrument in Multisim the LabVIEW Run-time Engine (RTE) version of the instrument must be installed on your computer.

We now have different versions of the instruments uploaded to the community page for the custom instruments and analyses (join it and get the most recent updates).

With Multisim 12.0.1 released on September the 14th of 2012, you get the RTE2012 automatically installed and can run all the updated versions of the instruments and analyses in Multisim.

If you are a Multisim 12.0 user you only have the RTE2010 and RTE2011 installed and will have to install the 2012 one manually.

We will always keep all the instruments up-to-date and available for download.

Please let me know your feedback and if you have any questions about installing a custom LabVIEW instrument for Multisim.

Mahmoud W

National Instruments


Hello Circuit Designers,

Digi-Key's search tool in Multisim provides you with updated information on part availability, pricing, and specifications from wihin your design toolbox.

As you're building your schematic, you could search for the components you're placing using this utility tool developed in LabVIEW and available for download here.

This is just one of many custom instruments and analyses developed in LabVIEW for the Multisim users. The LabVIEW Instruments bring advanced capabilities of signal generation, processing, analysis, and visualization to Multisim's SPICE environment. All these add-ons could be downloaded from the Multisim Custom Simulation Analyses and Instruments page.

Enjoy desigining!

Mahmoud W