Author Topic: Understanding Vcm vs Vout graphs for Instrumentation Amplifiers  (Read 1671 times)

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Offline ZeroResistanceTopic starter

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Understanding Vcm vs Vout graphs for Instrumentation Amplifiers
« on: February 15, 2019, 03:39:09 pm »
What is the significance of the Vcm vs Vout graph.
I am planning to use the INA826, and I stumbled upon a post https://www.edaboard.com/showthread.php?361259-Problem-with-Instrumentation-amplifier-Gain-INA826
regarding the same amp where the user was experiencing variation in gain when the output voltage crossed a particular threshold.

I intend to use the same chip and would like to understand the Vcm vs Vout concept clearly before going ahead with the circuit.
I am planning to power the chip @ 3.3V single supply and a gain of around 25, input would be in the range of 30 to 120mV so at that gain I would expect the output to vary between 0.75V to 3V.

I am attaching the graphs below.



 

Online iMo

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Offline ZeroResistanceTopic starter

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Re: Understanding Vcm vs Vout graphs for Instrumentation Amplifiers
« Reply #2 on: February 15, 2019, 06:21:48 pm »
http://www.ti.com/tool/ina-cmv-calc

That's an amazing link and amazing software. Although it is somewhat large for what its meant to do.
The most important information in there is the Help button imo!
However it was worth the download from a conceptual understanding point of view!

Many many many thanks!
 :-+
 
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Offline ZeroResistanceTopic starter

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Re: Understanding Vcm vs Vout graphs for Instrumentation Amplifiers
« Reply #3 on: February 15, 2019, 08:27:26 pm »
http://www.ti.com/tool/ina-cmv-calc

Somehow the software is showing a different graph from the one I posted above from the datasheet in my first post.
 :-/O

 


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