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Old 30th March 2009, 07:01 PM   #1
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Join Date: Feb 2002
Location: Germany
Question High input impedance X circuit

Hello Guys,

I'm looking for an X-circuit wich offers a high input impedance. All circuits I found up to know in this forum use the inverting inputs of the two individual amplifiers as an input. So I have drawn a circuit that with modified feedback path to free the J-Fet inputs. Very simple question (but maybe difficult to answer) "Is this still a X-circiut?" Curious to see your comments guys.

Best

Zelter
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Old 31st March 2009, 12:22 AM   #2
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What stabilizes the quiescent current in the output totems?
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Old 31st March 2009, 06:22 PM   #3
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Default Re: High input impedance X circuit

Quote:
Originally posted by zelter
Is this still a X-circuit?
No. If you introduce an error somewhere and follow it through,
it will not reproduce on the other side in phase.

Not that this isn't a good circuit concept - I have had occasion to
use it and it works fine.

X circuits have limitations on input impedance because the active
input terminals are operated as virtual grounds, kind of like an
inverting input op amp. If you want a really high input impedance,
it's easier to buffer the inputs.

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Old 31st March 2009, 06:28 PM   #4
EUVL is offline EUVL  Europe
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You can "X" the F5, and it still have high input impedance.

Patrick
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Old 31st March 2009, 10:06 PM   #5
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Quote:
Originally posted by EUVL
You can "X" the F5, and it still have high input impedance.
You can bridge the F5 sharing the feedback loop, but any error on
one side is amplified by the other side and becomes larger instead
of cancelling, so it would not be thought of as X.

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