pss simulation result interpretation

[shivaamordad]

hi
i have done pss simulation for an ideal switch
and plot the output voltage vs frequency
(actually i want to simulate a chopper stabilized amplifier and start with this simple circuit to understand pss simulation)

now i cant find out the meaning of the plot
in other word i want to know what i have measured (what is the amplitude of impulse in output spectrum)

the circuit and the output plot are attached

regards

 

[erikl]

Now, what did you expect? It's just what you ordered to be plotted: the output voltage's frequency spectrum. The transformation of the output pulses from time domain into the frequency domain - here accomplished by an FFT.

 

[shivaamordad]

hi erikl

thanks for your reply

you mean the pss compute the first 10( i have set the harmonic in pss to 10) Fourier series coefficient of the periodic square wave that we see in the transient analysis?
so why in pss when we plot the output vs time,it shows the complete square wave?
i think it should show just the first 10 term expansion of the square wave as i attached the picture

and an other question:
what is this spectrum relation to dc operating point,because i read that pss show the periodic dc op point?

thank you so much

 

[pancho_hideboo]

i think it should show just the first 10 term expansion of the

No. You use Shooting-Newton-PSS, so it calculates time-domain waveform directly.

If you use HB-PSS, time-domain waveform is calculated by Inverse FFT.

because i read that pss show the periodic dc op point?

Wrong.

See my append #7 in https://www.edaboard.com/threads/169169/

Generally there are two options for PSS.
One in based on Harmonic Balance(Kirchhoff's Low in Frequency Domain)
The other is based on Shooting Newton(Kirchhoff's Low in Time Domain)

Also see my append in https://www.edaboard.com/threads/195061/