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A Spice simulation question

I've entered the circuit for a "warble" audio oscillator! Basically the low freq (2Hz) part frequency modulates the high freq (1kHz) audio signal. I can see the resulting "FM" output.

In Spice I use

.trans 0.001s

and can use different times for s to see it more compressed etc. However is there a way to see the wave say 0.5s into the display? I mean start at say .49s and see a few cycles after that. If I use .trans it always starts at zero.

I don't think I'm explaining this too well... trying again... what I'd like to see is a few cycles, say the start of the output, then a few cycles some time later (so I can see the FM effect is actually working and measure the period on screen) Thanks

Reply to
dave
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The actual syntax might vary by the particular spice implementation, but in general the following syntax would apply:

.tran [Tstep] [Tstop] [Tstart] [DTmax]

and the short form (which you used) is: .tran [Tstop]

Tstep is the plotting increment for the data, not the timestep for the analysis. If set to 0, then the plotting increment equals the timestep.

Tstop is the ending time for the analysis.

Tstart is the starting time to record/save the analysis data. The analysis always starts with time=0. If Tstart is blank or zero, then the data is recorded from the beginning. If you set this value some something non-zero, then the initial results up to this time will not be saved. This is the parameter you want to use.

DTmax is the maximum timestep to use, so you can force a max timestep in the analysis, even for when signals aren't changing quickly.

Reply to
w2aew

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