What Multisum and Qspice actually do

Multisum and Qspice are both circuit simulation programs, but they approach the job differently. Multisum is a general-purpose SPICE simulator that runs on Windows and focuses on being straightforward to learn and use. Qspice is Analog Devices' newer simulator, also Windows-based, and it's built on a faster simulation engine designed to handle complex circuits more quickly.

Neither is the industry standard — that's still LTspice, which Analog Devices owns and distributes free. But both Multisum and Qspice exist because different engineers have different workflows, and sometimes a tool that's not the biggest can still be the right one for what you're building.

Key Takeaways

  • Multisum is easier to learn if you're new to circuit simulation, while Qspice is faster at running large or complex simulations.
  • Qspice is free from Analog Devices; Multisum requires a paid license, though free trial versions exist.
  • Multisum has a longer history and a larger library of third-party models; Qspice is newer and growing its component library.
  • Both run on Windows only — neither has native Mac or Linux versions.
  • Your choice depends on whether you prioritize ease of use and existing models (Multisum) or simulation speed and modern architecture (Qspice).

Speed and simulation engine differences

Qspice uses a newer simulation engine that Analog Devices built from the ground up. This matters when you're simulating circuits with thousands of components or running transient analysis on long time windows — Qspice typically finishes faster. The engine also handles certain types of nonlinear behavior more efficiently, which can mean the difference between a simulation finishing in minutes versus hours.

Multisum uses a more traditional SPICE engine. It's not slow, but it doesn't have the architectural advantages of Qspice's newer code. If you're simulating small to medium circuits — a power supply, an amplifier stage, a filter — you won't notice the difference. If you're simulating a full board with mixed-signal blocks, Qspice's speed advantage becomes real.

Cost and licensing

Qspice is free. Analog Devices released it free to use, and there are no seat limits or time restrictions. You download it, install it, and run it without paying anything or entering a license key.

Multisum requires a paid license. The company offers a free trial period (usually 30 days), but after that you need to purchase a license to keep using it. This makes Multisum a harder sell for hobbyists or students, though some educational institutions have site licenses that cover their students.

Component libraries and third-party models

Multisum has been around longer and has accumulated a larger ecosystem of third-party component models. If you work with older or specialized parts, or if you use models from specific manufacturers, you're more likely to find them already built for Multisum. The user community has also created many custom models over the years.

Qspice's library is growing but is still smaller. Analog Devices has prioritized their own parts, so if you're using Analog Devices components, Qspice has excellent support. For other manufacturers, you may need to find or create models yourself, or convert them from other SPICE formats. The conversion usually works, but it adds a step.

User interface and learning curve

Multisum's interface is designed to feel familiar to anyone who's used older SPICE tools. The schematic editor is straightforward, the menu structure is logical, and the documentation assumes you know what a SPICE netlist is. If you're already comfortable with circuit simulation, Multisum gets out of your way.

Qspice's interface is more modern and includes some quality-of-life features that Multisum doesn't have — better integration with the schematic editor, clearer error messages, and a more intuitive way to set up simulations. For someone new to SPICE, Qspice is usually easier to pick up. For someone switching from LTspice, Qspice feels more familiar because Analog Devices designed both.

When to choose Multisum

Choose Multisum if you have a specific component or model that only exists in Multisum format, or if your organization already has licenses and training invested in it. Also choose it if you're working in an environment where the simulation speed difference doesn't matter — most analog circuit work falls into this category.

Multisum is also worth considering if you need long-term stability and don't want to depend on a tool that's still being actively developed and changed. Qspice is improving rapidly, which is good, but it also means features and behavior can shift between versions.

When to choose Qspice

Choose Qspice if you're starting fresh and want a free tool with a modern interface. The zero cost removes a barrier, and the faster simulation engine means you'll spend less time waiting. If you use Analog Devices parts regularly, Qspice's library support is excellent.

Qspice is also the better choice if you're simulating large or complex circuits — power electronics, mixed-signal designs, or anything with thousands of components. The speed advantage compounds as circuit complexity grows. And if you're already familiar with LTspice, Qspice will feel natural because the two tools share design philosophy.

Frequently Asked Questions

Can I convert a Multisum circuit to Qspice?

Usually yes. Both tools use SPICE netlist format underneath, so you can export from Multisum and import into Qspice. Component models sometimes need adjustment, and custom symbols may not transfer, but the core circuit usually moves over without major rework.

Does Qspice work on Mac or Linux?

No. Qspice is Windows only. Multisum is also Windows only. If you need to run circuit simulation on Mac or Linux, LTspice is your free option, or you can use web-based tools like CircuitLab or EveryCircuit, though those have different capabilities.

Which one do professional engineers use more?

LTspice is still the most common in professional settings because it's free and has been around for decades. Multisum and Qspice are both used, but in smaller numbers. Qspice is growing because it's free and newer, while Multisum is mostly used by people who already own licenses or work at companies that have them.

If Qspice is free, why would anyone buy Multisum?

Inertia and specific models. Organizations that have used Multisum for years have invested in training and custom models. Switching costs time and money, so they stick with what works. For new projects, though, the free cost of Qspice makes it hard to justify Multisum unless you have a specific technical reason.