# Help resolving Instrumentation Amp.

Discussion in 'Homework Help' started by useless, Jul 25, 2004.

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1. ### useless Thread Starter New Member

Jun 17, 2004
5
0
Hello Gents
I am having a problem trying to resolve a circuit with an instrumentation amplifier in which the voltage applied to the top buffer circuit is 3v and +2v to the bottom one.
Is -5v the difference of potential? and 0.5mA the current? is the current flowing towards the top buffer?, if I am right on this, what is the difference of potential between the two outputs of the buffers?

2. ### Dave Retired Moderator

Nov 17, 2003
6,960
144
Assuming you are using a standard Instrumentation Amplifier, your source voltage will be the difference between the two rails, i.e. v1 - v2, which I assume is the 5V you talk of.

As for current, you will most probably be expected to assume ideal conditions, therefore the current is given by the source voltage divided by the resistance present between the inverting inputs to the two input op amps, Ri:

I = v1 - v2 / Ri

A diagram of your problem would probably make solving the problem easier.

3. ### useless Thread Starter New Member

Jun 17, 2004
5
0
Hello Dave,
Sorry for not making this clear enough, but it is the first time that I post a message to a forum....
The day after I post this this problem and I decided to use electronics workbench to find out if the calculations I did we right, and now it is solved.

Regards

4. ### Dave Retired Moderator

Nov 17, 2003
6,960
144
No problem, thanks for letting me know

Dave

5. ### sanjay agarawal New Member

Dec 6, 2014
3
0
i have implemeneted tweo op-amp based inst amplifier. one NI IS KEPT AT 100 MILI VOLT wrt to other.

i ma not gettin g 10.23 volt out put.

both op-amps are supplied at 12 volt dc. pin 11 is at grd.

Apr 5, 2008
15,533
2,300
Welcome to AAC.

Congratulations, you have practiced the arcane art of necromancy, the revival of a long dead thread. Likely the OP (Original Poster) has solved his problem in the years that has passed, or thrown it away, or something.