Circuit Parameters to Make Schematics Smarter

Oct 01 2013, 12:25 PM PDT · 3 comments »

CircuitLab now supports parameterized circuits, allowing you to define variables and have one or more circuit elements depend on those values. To add a parameter, find the "Parameter Element" in the toolbox, and set a name equal to a value. For example, "Rsrc" = "500" to create a variable with name Rsrc and value 500. You can subsequently reference the name Rsrc in any circuit elements you wish, and before running the simulation, the CircuitLab engine will compute and replace the parameter for you.

These sheet-wide parameters can include calculations, and can even reference each other. In effect, we've built a programming language layer to give you more control of your simulations!

This powerful feature can be used to drive simulations, sweeping multiple related values simultaneously, and can even calculate useful component values for you.

For a simple example, see a parameterized op-amp non-inverting amplifier, which calculates its own resistor divider values:

Open and run the simulations to see the gain-bandwidth tradeoff and the calculated resistor values!

For a more advanced example, take a look at this RF Matching Network, which calculates the correct inductor and capacitor value to use to perform an impedance match between source and load at 2.45GHz:

Open and run the simulations to see the narrowband power transfer maximum across frequency and the calculated capacitor and inductor values!

We hope you'll enjoy this powerful capability and push your simulations to the next level.


Rotate Node Names (It's About Time!)

Sep 30 2013, 7:30 PM PDT · 0 comments »

Node Names can now be flipped and rotated using the existing controls. No more awkward placement of node names!


Piecewise Linear and Step CSV Sources

Sep 30 2013, 6:00 PM PDT · 1 comment »

Need to inject a custom signal into your simulation? CircuitLab has long allowed piecewise linear and piecewise step sources, but we've now added a CSV source to the toolbox. You can now paste in a larger CSV file of (time,voltage) pairs, one per line, and the simulator will use your input for simulation.

Our first example is a multilevel inverter with a piecewise-step sinusoidal-like signal, and applied low-pass filtering:

Our second example is a simple switching power supply with a edge-defined gate drive signal and a digital inhibit feedback loop:

Try out these simulations and double-click the CSV sources to look at their contents!


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CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.