ltspice simulation

Drive and organize your analog simulation more effectively

In our increasingly digitized world, analog circuits show no sign of diminishing. Mixed analog/digital designs are very common. Sensors, controllers and multimedia interfaces all include analog circuits.

Traditionally, analog analysis has been separate and tackled by specialists. There’s no substitute for expertise but keeping data in a different place is never a good idea—especially when there are engineering changes or enhancements.

With Schematic Editor SPICE Controller, you can set up simulation directly and that setup stays with your schematic design.

Once you are simulating with LTspice, there is no substitute for experience and its extensive, freely available online information. But keeping the setup with your design data and closely linked to it makes tasks like AC analysis and corner case checking parts of a joined-up process.

Best-in-class analog simulation for your PCB designs

Schematic Editor SPICE Controller provides enriched integration, as well as ideal facilities to explore design options while keeping your setup with your schematic.

  • Use the leading, proven analog simulator LTspice while keeping key data with your eCADSTAR schematic
    • The LTspice SPICE circuit simulation software is free to download and use
  • Explore operating ranges and passive component values dynamically, even if you have not yet assigned production parts. Decide on the tolerances, wattages, etc. that you need to make your design both economical and robust
  • Perform Monte Carlo analysis to check for random combined-effect issues that can put your analog circuit’s performance out of specification, without the number of simulations getting unrealistically high.

Preserve and recall settings easily with built-in simulation control

You can simulate parts of your schematic or your whole design. It is usually more useful to focus on specific circuits. LTspice models have their own pin numbering conventions. As well as mapping to the correct pins to simulate components like transistors, diodes and operational amplifiers, you can override the values of passive components like resistors and capacitors. You can, for example, explore the effect of different bias levels, passive filtering or alternate independent voltage sources.

simulation setup and LTspice model pin assignments
You define the simulation setup and LTspice® model pin assignments directly in Schematic Editor. This means the setup data stays safely with the design instead of being separate.

Simulate your analog circuits with powerful, industry-proven methods

Once you have set up the simulation parameters, you can save and re-use them for the same schematic. The simulation parameters are paired with the simulation netlist you generate, so they are valid only for that circuit. Once LTspice simulation is running, you have all the facilities that it offers.

simulation netlist
This simulation netlist is for one sheet of the schematic: an audio amplifier circuit. You can also simulate framed areas of your schematic or your whole schematic.
simulation of an audio amplifier
In this simulation of an audio amplifier, the lower, red traces show the amplitude of the input signal being swept in 0.1 Volt steps. The corresponding blue traces above show the response at the speaker output. You can see at what input level the output stops clipping. In audio terms, this would be the point at which a guitarist stops sounding as though they are using a fuzz box.

Roll the dice before production and beat the odds of a surprise

As its name suggests, Monte Carlo analysis is about rolling the dice. What will happen if multiple things over which we have no control vary at random and simultaneously? What if the environment is particularly hot or particularly cold and at the same time, one or more of the components is operating at the limits of its specification?

Simulating all situations where there are multiple variables means a very large number of simulations. If you roll two dice at Monte Carlo, they can land in 6×6=36 different ways. If you have, say, five variables, each in ten different states, then your number of simulations would be 10×10×10×10×10=100,000.

The beauty of Monte Carlo analysis is that instead of simulating all values, it intelligently randomizes which values to consider based on mathematical statistics.

Here is a simple example: checking the effect of a ten percent versus a one percent tolerance for the input and output resistors of an operational amplifier. You choose the number of samples and variations in the two values are distributed intelligently to show the variation in output without having to simulate every case.

parameter_spie controller
The two resistor tolerances are set by these parameters. For the first Monte Carlo simulation, they are set to 0.1, which represents a 10% tolerance.
a 1V drift in output amplitude
There is about a 1V drift in output amplitude as both resistors drift from their ideal values—too much for this circuit. The setup created within SPICE Controller in Schematic Editor is shown in LTspice® form in the same view.
a 1V drift in output amplitude
There is about a 1V drift in output amplitude as both resistors drift from their ideal values—too much for this circuit. The setup created within SPICE Controller in Schematic Editor is shown in LTspice® form in the same view.
resistor tolerances are set to one percent
When both resistor tolerances are set to one percent, the same Monte Carlo simulation shows a very small output amplitude drift, so one percent tolerance resistors are chosen for this circuit.

What Schematic Editor’s SPICE Controller gives you and how best to use it

Why not just use LTspice directly? You can add and connect components right there and simulate them. There is no reason why you should not do that too, but SPICE Controller keeps the simulation setup with your schematic design and links simulation to your schematic design data. That makes LTspice simulation cases both easier to manage and easier to set up. It closes the loop between your schematic design and your LTspice analysis in a way that means you can retrieve it later.

The recommended way, preferred by many analog engineers, is to create separate mini designs in Schematic Editor that they can use as design building blocks, together with their simulation setups. These can be imported into different schematic designs while keeping the reference copies of the analog designs separate. If an analog designer enhances one of these circuits, it will be available as an upgrade to designs that use it at a time of your choosing.

Here is a demonstration that goes deeper into LTspice simulation from Schematic Editor


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