kicad-developers team mailing list archive

[Jonatan Liljedahl <lijon@xxxxxxxxxxxx>]

On Wed, Oct 14, 2020 at 8:00 PM pepijn de vos <pepijndevos@xxxxxxxxx> wrote:
...
> For example, two other things that would be great to add is a way to plot algebraic expressions of different signals, to plot things such as impedance and transconductance, and a way to annotate operating points in the schematic. But these are probably a lot more work, and also require some more in-depth design discussion.

Actually you can plot algebraic expressions. Here's an example from my
experiments with checking phase margin of op-amp circuits etc:

.ac dec 20 10 10Meg
.control
  set controlswait
* calculate loop gain, noise gain, open loop gain
  let AB=V("/m2")/V("/m1")
  let B1=V(out)/V("/m2")
  let Aol=V(out)/V("/m1")
* print out cross-over frequency and phase margin
  let dbAB=db(AB)
  let phAB=180/pi*ph(AB)
  display
  meas ac unitf when dbAB=0
  meas ac phm find phAB at=unitf
.endc

Some things to note here are that local labels in eeschema will have
"/" in their names and thus must be quoted, also the new signals AB,
B1 and Aol won't show up in the signal list, but you can still add
them manually by entering their name in the textbox below the list!
(Actually I added that textbox specifically for this purpose, but it
also works for quickly adding a signal with known name instead of
having to scroll around in the list)

Cheers

-- 
/Jonatan
http://kymatica.com