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electronics_kumar
Joined: 29 Nov 2004
Posts: 664
Helped: 26
Location: Tamilnadu
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 15 Feb 2006 11:43 output offset voltage! |
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| among all chracteristics for an ideal op-amp,i encountered that output offset voltage is always is always zero...how it is possible
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puviarasu
Joined: 17 Dec 2004
Posts: 157
Helped: 7
Location: India
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15 Feb 2006 11:48 output offset voltage! |
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Do you mean ideal opamp , in that it is the definition.
for practical characteristics of op amp it will be very less or nil as opamps now are very precise.
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the_risk_master
Joined: 12 Aug 2005
Posts: 688
Helped: 59
Location: UE+MIT, Philippines, (14°N , 120°E )
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15 Feb 2006 11:52 Re: output offset voltage! |
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It is due to the CMR of the differential stages
(Ideally offset is zero)
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15 Feb 2006 11:52 Ads |
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vdaniel
Joined: 08 Oct 2004
Posts: 216
Helped: 9
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15 Feb 2006 12:45 Re: output offset voltage! |
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By definition, the output voltage of an ideal OA is
Vout = g*(V+ - V-)
where g -> eternity
For real OAs, the formula looks like
Vout = g*(V+ - V- + Voffset)
The easiest way to measure Voffset (for unity stable OAs) is to connect the inverting (V-) input to output, and the non-inverting input to GND. The output voltage will be equal to Voffset.
For real OAs, Voffset can be in range from microvolts (for chopper stabilized OAs) to millivolts.
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kohtwe
Joined: 16 Jan 2006
Posts: 22
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26 Feb 2006 16:36 Re: output offset voltage! |
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Hi!
all chracteristics for an ideal op-amp, encountered that output offset voltage is
always zero, it is possible because offset voltage can be noise
but offset voltage (+V/ -V) use op-amp
Goodluck
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lavitaebelle
Joined: 26 Jan 2006
Posts: 75
Helped: 11
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26 Feb 2006 20:55 output offset voltage! |
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Offset consists of two parts, systematic offset and random offset. Systematic offset is due to mismatch in device sizing, currents,non symmetry,etc. Random offset is due to device property mismatch such as Vt,effective W,L.
For any opamp designed symmetrically, there will be no systematic offset. Random offset is a statistical parameter, depends on the statistical variation of the device properties.
Of course in an ideal opamp, there is no systematic or random offsets and hence no offset.
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