Designing electronic circuits takes knowledge and experience. Sooner or later, you have to put your idea to the test. Generally, this means building a prototype. Even with the best circuit simulator software, you ended up with unfriendly or expensive products. Or both. Now you can do a good job with an online circuit simulator tool to test your ideas.

The online circuit simulator from Circuit Labs is a web based circuit modelling solution. It can simulate a wide range of electronic components from simple passive devices like resistors and capacitors all the way up to complex integrated circuits. In fact, you could do the electronic design, and modelling for  your own integrated circuits if you wanted to.

The interface is a delight to use with a palette of sample components readily available. You can easily drag and drop components into your circuit, connect them up, label nodes and specify measurement points. A variety of input sources are provided. Not only do you get the obvious, like voltage sources and current sources, you can make voltage controlled current sources, digital clocks with variable duty cycle. and any combination of these. It didn’t take too long to work out how to make a reasonable model of a phototransistor for example.

Better yet, there is a library of existing designs created by other for you to examine and experiment with or to use as the basis for your own efforts.

Once your electronic circuit is all placed and connected up, you can run several different kinds of simulation. A straightforward DC analysis will let you check quiescent currents and bias levels Then you can move on to frequency response plots or time domain simulation to see how the circuit responds to transients.

A single transistor amplifier example

A simple single-transistor amplifier circuit might look like this:

A Simple transistor amplifier for online simulation

DC analysis of the circuit gives us the following value:

results from the DC analysis of the transistor amplifier

I will leave it to you to verify that these are exactly what we might expect. Now, an AC analysis can be done to get the overall frequency response of the amplifier. Again, I leave it to you to work out that the results are as expected:

frequency responce of the single transistor amplifier.

There is a lot more that you can do with this online circuit simulator but here is one more interesting possibility. It is easy to see the effect of changing a component value. Here I have told the simulator to perform the AC analysis with various values for the collector resistor, R3. This will change the amplifier’s gain but will also affect the amplifier’s bandwidth.

effect of changing the collector resistor in a single transistor amplifier

And the best bit? Well, at the time of writing, this is all free. Not free as in beer but free as in no money.

Also, in case you don’t think Oracle has your best interests at heart, it does not use Java.

You might want to test out your design skills by working out what happens to the response when R3 is large (9000 Ohms).

Visit the site and have a look for yourself:-

This Post Has 5 Comments

  1. Limak

    Oh yeah! Great online tool – thanks:)

  2. Edo. Franzi

    Great idea. For OSX users, maybe a real spice application could be a better solution.
    Here is a beautiful OSX implementation of spice

  3. Peter Harrison

    Volta does have many good points and the price is friendly. For me though, it needs more work. It was not clear how to show component values on the schematic and you seem to have to already know how to use spice-type tools to get stuff to work. This is probably great for the experienced user but less so for the newcomer or casual user.

  4. Selina

    Hey Peter,

    Circuitlab is not free now. Do you know EasyEDA? A new free web-based EDA tool, EasyEDA was designed by a team of hackers for five years. Result: a free and powerful software used on all computers from Chrome, Firefox, IE, Opera, or Safari.
    It offers schematic capture, spice simulation and PCB design – including Gerber download – for free.
    It also offers low cost PCB manufacture and assembly.

  5. Peter Harrison

    Thank you. I will have a look at that.

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