Re: Simulation Device... Keyed Peak Detector
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Posted by John Larkin on May 29, 2008, 2:42 pm
Please log in for more thread options >>Jim Thompson wrote:
>>> 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 | |||||||||||||||||||
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Posted by Chuck Harris on May 29, 2008, 3:39 pm
Please log in for more thread options >>> 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? 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 | |||||||||||||||||||
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Posted by Helmut Sennewald on May 29, 2008, 5:12 pm
Please log in for more thread options
> On Wed, 28 May 2008 14:51:12 -0700, Jim Thompson
> >>On Wed, 28 May 2008 14:27:16 -0700, Joerg
>> >>>Jim Thompson wrote:
>>>> 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. Hello John, try this one in LTspice. .model DID D(Vfwd=0 Ron=1m Roff=1G) Best regards, Helmut > Hey, why not make an ideal diode from a voltage-controlled switch?
> > John > > | |||||||||||||||||||
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