Re: gEDA-user: How to?

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Tuesday 12 July 2005 11:05, Harold D. Skank wrote:
>People,
>
>This questions sounds pretty basic for someone who has been around
> SPICE as long as I have.  I first ran SPICE when I had to submit
> the circuit on punched cards for simulation on an IBM 7074.  Had to
> wait about a day to get the results back on line printer paper. 
> Well, on to gEDA questions.
>
>I have created a state variable BP filter.  I can run the ac
> analysis using ngspice, and that seems to work very well.  It has
> allowed me to specifiy the circuit values to get the band shape
> that I need.  Now though, I would like to see the circuit response
> to a 5-cycle truncated sine wave input, since this is the "real"
> signal that the filter will see in operation.  How do I specify
> this as a voltage input and how do I actually run the simulation?
>
>Sounds dumb, huh?
>
> Harold Skank

Just off thet op of my head, Harold, a state variable BP filter is 
usually going to have too high a Q factor to adequately respond to a 
5 cycle burst.  I think, if I wanted to detect that, I'd time the 
zero crossings and keep a running average after the first one.  From 
that you can get the reciprocal which is the frequency * 2.  If its 
the right frequency * 2 at the end of the allowed 5 cycle burst time, 
then its a valid signal.

-- 
Cheers, Gene
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