1. Background
There’s no shortage of circuit simulators available to ECE undergraduates, and many of them end in Spice. Most notable are PSpice and LTSpice, but like Linux distros, there are a plethora of circuit simulators available, and it’s difficult to discern which circuit simulator is right for you.
| Unlike Linux, Hannah Montana does not have a circuit simulator bearing her name. |
CircuitLab is a common one, and rightfully so. You can make a circuit and simulate it in five minutes flat. But I’ve found that there are certain aspects to CircuitLab that make it pretty annoying:
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It’s not free. Even though I can use it for free now, I want something that I can use for the rest of my life, at no cost to me.
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Keyboard shortcuts are not intuitive. I don’t want to go to the search bar every time I want to place a resistor. It’s literally the most common passive component in the undergrad curriculum! Why can’t I just press the R button and get a resistor?!
There are a couple of things I value in a circuit simulator:
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Price: If I’m going to pay for a circuit simulator, it had better be the most convenient, most efficient, knock-your-socks-off circuit simulator.
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Keyboard friendliness: If I have to click on 20 buttons just to place a voltage source, I’m looking for another circuit simulator.
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Convenient simulation and CSV export: I don’t know about you, but I don’t simulate circuits for fun. I want to extract information from the circuit, and a good ol' CSV file is the best way to do it.
CircuitLab and PSpice cost money and neither offers a satisfactory product for my purposes, and LTSpice has user-friendly keyboard shortcuts and exporting a CSV is easy enough. Last year, a new circuit simulator came out: QSpice. It’s a free download, similar to LTSpice, and shares many of the same design quirks with LTSpice. (Admittedly, QSpice looks like it was designed in the 2010s, a step up from the 2000s design of LTSpice.)
Since LTSpice and QSpice are free, have convenient (or programmable) keyboard shortcuts, and have relatively easy CSV exporting, I’ll share the pros and cons of each, from the perspective of an undergraduate EE student:
2. Keyboard shortcuts
Admittedly, I haven’t used the default keyboard shortcuts of LTSpice; I’ve used Prof. White’s LTSpice keyboard shortcuts, but they’re pretty intuitive, and the programmability of LTSpice’s keyboard shortcuts are very nice. For example, you can place a resistor, capacitor, and inductor with the R, L, and C keys respectively.
However, QSpice has most of LTSpice’s shortcuts, and more! Tragically, LTSpice has no "Place Transistor" hotkey; you have to hunt through the catalog for the right thing. Contrarily, QSpice has several transistor hotkeys:
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Q places a BJT
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M places a MOSFET
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J places a JFET
In QSpice, you can also repeatedly press a key to see variants of that element. For example, you’d see pulse, sine, and exponential voltage sources if you repeatedly press V. Likewise, repeated Q presses give you NPN, PNP, and other more obscure BJTs. Similarly, repeated M presses give you NMOS and PMOS. You even get the four-terminal kinds!
3. Simulation
3.1. Generating the SPICE Directive
Telling the computer what to do is often the most difficult part of operating a computer; once the computer knows what to do, it can typically execute its task within less than a second.
While LTSpice has a convenient and easy-to-use graphical interface, QSpice forces you to write the directive yourself. It gives you syntax hints, though:
Once you complete the SPICE directive, you’ll get Mike’s seal of approval:
3.2. Simulation
While LTSpice’s "Run Simulation" button remains unrivaled, there’s no functional difference between the simulations for an undergrad just trying to make sure their answers to their homework assignment is correct.
There’s also little functional difference in the CSV exporting process, though LTSpice is marginally better since it lets you choose where to export the CSV.
4. The Verdict
Barring any quality-of-life updates from QSpice, it’s a dead heat for these programs. If you like aesthetics, you’d probably consider QSpice the lesser of two evils. If you’re into the simulation side of things, LTSpice’s GUI and slightly more user-friendly CSV exporting probably lure you into the LTSpice camp. If you’re building circuit after circuit and you want a program that streamlines that process, QSpice easily takes the cake.
In my experience, though, QSpice’s data exporting isn’t too much of a hassle, and the constant hunting for the right transistor in LTSpice gets annoying very quickly. So QSpice is my circuit simulator of choice.