LTSpice question

[lordvader88]

I'm getting the hang of LTS, I made the linear PSU from my Tektronix 422 and it works perfect.

When u make a circuit, and you have to find DC operating points, do u have to run DC op.point every time u change a value ? I see when I run transient sim, that I can change a value, and just hit run again, and it makes the changes. Does that update the saved DC op.point as well each time ?

[Zero999]

Running the transient simulation, updates the DC operating point, unless the "skip initial operating point solution" or "start external DC voltages at 0V" is selected.

The .step command can be used to run simulations for different values of the same component(s) without having to manually keep editing them and rerunning the simulation.

Here are a couple of simulations I've done recently, using the step command, to emulate a variable resistor.
https://www.eevblog.com/forum/beginners/need-assistance-in-calculating-resistors-in-a-differential-amplifier/msg2331510/#msg2331510
https://www.eevblog.com/forum/beginners/simple-transistor-impedance-understanding/msg2221683/#msg2221683

[T3sl4co1l]

It's always done automatically, unless you turn on "save op point", or disabled completely as mentioned.

Tim

[Zero999]

A demonstration showing a simplified model of the LM317, with both resistor values swept. R1 from 50Ohm to 200Ohm, in 25Ohm steps and R2 from 10Ohm to 1500Ohm in 100R steps.

Note, the file size of the schematic converted to an image can be reduced by converting the colour depth to <8-bit, removing the alpha channel and saving as PNG.