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negromonte1
Guest
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 Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Ideal op.amp: vid=0 question |
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I don't understand a thing. Why vid (volt inputs differential)
is null, only when op.amp. works in linear zone?
Thanks in advance.
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John Popelish
Guest
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| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: Ideal op.amp: vid=0 question |
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Opamps have very high differential gain when their outputs are not
saturated either positive or negative. So it takes a very small
differential voltage times all that gain to keep the output voltage
not saturated fully positive or negative.
Therefore, the simplifying assumption is that if the opamp is in the
linear (not saturated output) range, the differential input voltage
must be approximately zero. |
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Rene Tschaggelar
Guest
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| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: Ideal op.amp: vid=0 question |
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Because the output voltage is almost infinite
times the input voltage differential.
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
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Dan Hollands
Guest
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| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: Ideal op.amp: vid=0 question |
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If the vid was zero the opamp would be operating in the "linear zone"
The only reason it is not zero is if the opamp can not drive the output far
enough to make it zero
--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhollan3@rochester.rr.com
www.QuickScoreRace.com |
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Paul Burke
Guest
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| Posted:
Tue Dec 06, 2005 5:35 pm Post subject:
Re: Ideal op.amp: vid=0 question |
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Because the ideal opamp has infinite gain, and anything multiplied by
infinity is infinity. In engineering we tend to use infinity when we
mean a very large number, sometimes even as big as 255.
Paul Burke |
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neon
Joined: 25 Feb 2006
Posts: 594
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Sat Mar 18, 2006 2:37 pm Post subject:
Re: Ideal op.amp: vid=0 question |
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if you tie one dif. input to let say gnd then other input will be ground or actualy virtual gnd to satisfy the input. when in the linear mode no matter what the gain is and no matter what the input volts is those two inputs will remain at virtual gnd that is the craiteria for an op-amp. there are offset voltage and offset current to contend with but that is the princable anyhow.
| negromonte1 wrote: | I don't understand a thing. Why vid (volt inputs differential)
is null, only when op.amp. works in linear zone?
Thanks in advance. |
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