Is LTspice really free with no real limitations?

Yes. LTspice is free from Analog Devices (which acquired original developer Linear Technology) with no seat limit, no time-limited trial, and no meaningfully crippled feature set for typical analog and power electronics simulation work. This is a real reason it remains the default free SPICE tool for students and practicing analog engineers, in contrast to PSpice, which offers only a capability-limited free student edition and requires a paid commercial license for full model libraries and advanced analyses like Monte Carlo simulation.

What is the actual difference between LTspice and PSpice?

Both are SPICE-based circuit simulators built on the same underlying simulation approach, but LTspice is completely free and ships with an enormous library of real op-amp, regulator, and power-management device models from the Analog Devices/Linear Technology catalog, making it especially strong for power electronics and general analog design. PSpice, owned by Cadence and historically bundled with OrCAD, is common in academic courses and legacy industrial workflows built around OrCAD decades ago, but its full model libraries and advanced analyses require a paid commercial license.

Why is my LTspice simulation failing or giving obviously wrong results?

The most common beginner cause is a missing ground reference — every SPICE simulation needs exactly one node designated as node 0 (ground/reference), and a floating circuit with no ground connection will fail to simulate or produce nonsensical results. Other frequent causes are a wrong or missing simulation directive (an incorrectly typed .tran, .ac, or .dc command), a component value entered with the wrong unit suffix, or a genuinely unstable circuit (like an oscillating feedback loop) that the solver struggles to converge on — each of these produces a distinct, recognizable error or warning in LTspice's output log worth reading carefully rather than skipping.

Can LTspice simulate digital circuits, or is it only for analog design?

LTspice is fundamentally an analog SPICE simulator, but it does include basic digital gate and behavioral models sufficient for simulating simple mixed-signal circuits, like a comparator driving basic logic. It is not built for large-scale digital logic simulation the way a dedicated HDL simulator (for VHDL or Verilog) is, so for anything beyond simple mixed-signal interfacing, a purpose-built digital simulation tool is the more appropriate choice.

Do I need to write SPICE netlist syntax by hand to use LTspice?

No, for the large majority of everyday use. LTspice's schematic editor lets you wire up a circuit visually with a mouse, placing and connecting symbols the same way you would in any PCB schematic tool, and it generates the underlying SPICE netlist automatically. The netlist is always viewable and directly editable if you need finer control over a specific simulation directive or component parameter, but hand-writing an entire netlist from scratch is rarely necessary for typical circuit design and validation work.

What is the benefit of simulating a circuit in LTspice before building it on a breadboard or PCB?

Simulation lets you catch design errors — an unstable feedback loop, a transistor biased into the wrong operating region, a filter with the wrong cutoff frequency — while changes are essentially free, since editing a component value and re-running a simulation takes seconds. Finding the same error after a physical board has been etched and assembled is far more expensive in time and money, which is why simulating first in LTspice is standard practice before committing a design to a real PCB, a workflow covered in more depth in the companion PCB & EDA software comparison article on this site.

Design·8 min read·July 22, 2026

📈 LTspice Tutorial: Free SPICE Circuit Simulation

A practical getting-started guide to LTspice: building a schematic, running transient, AC, and DC sweep simulations, reading waveforms, and catching circuit design errors before you build the physical board.

📖Engineering Software Handbook (Full Access)

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What LTspice Is

LTspice is a free SPICE-based circuit simulator originally developed by Linear Technology and now maintained by Analog Devices after its acquisition of Linear Technology. SPICE (Simulation Program with Integrated Circuit Emphasis) itself dates back to the University of California, Berkeley in the early 1970s, built as a way to mathematically predict how a circuit behaves before committing it to physical hardware. LTspice's specific appeal is that it packages real SPICE simulation into a fast, genuinely free tool with an enormous built-in library of real op-amp, regulator, and power-management device models drawn from the Analog Devices/Linear Technology catalog — which is a major reason it remains the go-to free tool for analog and power electronics designers despite commercial alternatives like PSpice existing.

Topics covered

LTspice tutorialSPICE circuit simulationLTspice transient analysisLTspice AC analysisfree circuit simulator