Diode uden spændingfald - Page 2

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Re: Diode uden spændingfald UDDYBNING

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Det er faktisk det du har. OPAMPen kompenserer for diodens
spændingsfald. Men både din diode og din OPAMP skal være _hurtige_ -
og di transistor til at aflade kondensatoren med vender forkert. Den
vil nok fungere alligevel, især ved lave spændinger, men du risikerer
læk i EB strækket.

Desuden SKAL du have negativ forsyning for at få det til at fungere,
din OPAMP vil ikke fungere korrekt så tæt på 0.


--
Ole Geisler, fejlfinder af Guds naade
Aut. baatnakke, flueknepper og universalgeni
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Re: Diode uden spændingfald UDDYBNING
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Et trick som man bruger normalt er at sikre at din opamp udgang ikke går i
saturation (til nul), så går der for lang tid hvis den skal op til niveau
igen

Her:

"
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easily

I have very strong doubts on your last statement about opamps not
operating at signal frequency, unless I have misunderstood your
comment........time passes........
However, after looking up my HnH 2nd Ed p889+891, I believe you ;)
Where have all the clever ccts gone.
"

Her:

Peak detectors can be tricky.  You can use a high slew rate op-amp, or
operate a comparator in its linear region.  Take a look at:

http://www.linear-tech.com/pdf/dn61.pdf

og sidst:

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supply
this

I think this is correct.

This circuit does have a small offset, depending on how you choose the
resistor values, but is quite a good "precision" rectifier at the higher
frequencies were opamps usually run out of steam.



/Klaus



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