--- In LTspice@..., rainbowsally <rainbowsally@...> wrote:
The .four or .fourier spice directive using the syntax in the docs does
not appear to work correctly.
When I create a net label named "OUT" and set the directive like so:
".fourier 1k v(out)"
ltspice says it can't find v(a) for the fourier analysis of THD. If I
then add a net label 'A' along side of 'OUT', it then computes the THD
correctly for node A but issues an error:
--> .fourier quantity "V(out)" not pressent in data.
If I remove the v(out) from the .fourier directive like so:
".fourier 1k"
It then works perfectly with the net label it appears to demand.
Either the docs are wrong or the program is broken.
Incidentally my third hack at kevin's amp at 100 W is Total Harmonic
Distortion: 0.052534% if we can believe that. But the components are not
final ones because I haven't yet looked at power issues with the ones used.
Also d/loaded texas instrument's tina. I like ltspice better though
tina is prettier and has a few features like 'temperature' testing that
are missing in ltspice. But tina apparently can't do THD calculations
at all.
To test THD for an amp the workaround in ltspice is as follows.
Add a spice directive (edit->text) ".four 1khz" (typically) and run the
transient analysis. Type 'ctrl-l' to view the log and scroll down to
the bottom of the fourier series to see the THD.
Works great! ...I think. Only checked one amp so far tho.
Hello,
I just tested the FOUR command. It has worked without problems.
I am sure you did something wrong in your schematic. I used
version 4.15s of LTspice.
.FOUR 1k V(OUT)
If you still have problems, then upload your schematic.
I will then check it.
Best regards,
Helmut
