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Opamp input common mode voltage (Read 596 times)
neuro11
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Opamp input common mode voltage
Mar 17th, 2013, 8:23pm
 
I am little confused about Opamp input common mode voltage. what i learned from a tutorial is this.

VICM = [VIN (+) + VIN (–)]/2

and

VICMR = VICMR_MAX – VICMR_MIN

Where:

VICMR_MIN = limit relative to VCC – supply rail

VICMR_MAX = limit relative to VCC+ supply rail

But thats not clear to me. Can someone explain the two parameters with some values.

Thanks in advance.
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raja.cedt
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Re: Opamp input common mode voltage
Reply #1 - Mar 18th, 2013, 12:43am
 
hello,
you are confused with two.
Vicm gives common mode when you signals applied. It is nothing to do with opamp architecture.

Vicmr_max means how max common mode you can apply to opamp and vicmr_min means how min common mode you can.

Always applied input common mode must fall in the range of vicmr_max-vicmr_min.

There is slight modification between the terms in your post and my reply, but you better follow this. Please have a look on Razavi book.

Thanks,
Raj.
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neuro11
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Re: Opamp input common mode voltage
Reply #2 - Mar 18th, 2013, 1:39am
 
hi Raj,
thanks for nthe clarification. I can understand now.
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