#222 inaccurate .ac analysis

[Anonymous]

I write a simple low pass filter, 1VAC on input:

*asdf
vac in 0 ac 1
r in out 1000
c out 0 0.000001
.ac dec 100 10 10000
.plot out
.end

I expect that output signal is 0.7 when frequency is 159Hz (f3dB=1/(2piRC)), but on the ac simulation this is 105Hz. I've got this results on ngspice-24 and ngspice on-line, pspice shows correct result (amplitude 0,7 with 159Hz). Transient analysis with sinus in ngspice also gives correct result. I suppose sth is wrong with .ac analysis. It works strangely also with other circuits I've simulated, the same simulations on pspice looks ok.
My operating system - linux mint 11.

Pozdrawiam
Michal Stec

[Robert Larice]

Hello Michal

in ngspice v(out) is a complex value
and
plot out
plots the `real' part of this.

try
plot abs(v(out))

Robert