Solving OPAMP circuit - need help

[txescientist]

Hi,
I need help solving one circuit - ideas, methods, anything. Know how to solve basic opamp circuits, but this I can't solve 

All parameters are known, I need to solve for Ip.

Any help is very much appreciated 

[electronics man]

Need more information

[txescientist]

I don't have any more information. We work just with variables, no numbers. Need to find current trough Rp. Tried with node potentials, but can't get solution. Maybe use superposition - Vi1 = 0 and find part of Ip1 and then use Vi2= 0 and get Ip2, so Ip = Ip1 + Ip2. I study physics, so we rarely use real numbers, just get equations and relations.

Thanks

[Rudane]

I think he's hinting at what you are suppose to relate. Should the answer be only a function of V1, V2 and R?

[txescientist]

That's right. Sorry for my confusing post. We only worked on class simple examples where inputs were not connected together and those examples are easy, but this I can't handle. Thanks

[IanB]

Label the unknown voltages at each of the nodes as V3, V4, V5, etc. (much as you did with V0).

Write current balance equations around these nodes to get some simultaneous equations. Assume the voltages at the op amp inputs are equal to get another equation.

Eliminate voltages from these simultaneous equations to get an expression for the unknown current Ip.

There may be a shortcut way of solving this problem (I'm not sure), but the above way is the first principles method that should work. It is just a lot of algebra.

[txescientist]

Solved it! Thanks for help!