Re: Simulation Device... Keyed Peak Detector

May 29, 2008 2 Replies


>


>>Jim Thomps>>> I want to build an ideal device for use in PSpice simulations, a Keyed
>>> Peak Detector...
>>>
>>
>>Ask someone at IPCC. They'll find every peak even if it ain't there :-)
>>
>>SCNR.
>>
>>
>>> Finds the maximum peak value of an input voltage while it's enabled
>>> ("keyed"), and "dumps"/outputs zero when not enabled.
>>>
>>> Any ideas?
>>>
>>> (Ideal elements)
>>>
>>
>>Aside from math, can't you use a buffer with (near) zero Zout, an ideal
>>diode, a wee cap? Then when it's keyed off use a FET with 1 femto-ohm
>>Rdson to short out the cap.
>
>Except that ideal diodes tend not to converge. I'm looking for some
>mathematical method that is "smooth" ;-)
>
> ...Jim Thompson

Why not fudge a regular diode to be almost ideal, and put a gain of a million in front?


LT Spice doesn't seem to have an ideal diode.


Hey, why not make an ideal diode from a voltage-controlled switch?


John


Well, that is the usual way that one makes an "ideal" diode in the real world... put a real diode in the feedback path of an opamp and let the negative feedback take care of the details.

-Chuck

"John Larkin" schrieb im Newsbeitrag news: snipped-for-privacy@4ax.com...

Hello John,

try this one in LTspice.

.model DID D(Vfwd=0 Ron=1m Roff=1G)

Best regards, Helmut

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