# op-amp circuit question

Discussion in 'Homework Help' started by gonzasvydd, Nov 30, 2014.

1. ### gonzasvydd Thread Starter New Member

Nov 30, 2014
4
0
For the circuit below, determine VOUT where R1=R2= 10 KΩ, R3 =100 KΩ, R4= 30 KΩ,
R5=40 KΩ, R6=30 KΩ, VS1=VS2= 2 volts.

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2. ### MrChips Moderator

Oct 2, 2009
14,496
4,268
The rules for Homework Help are we don't do your work for you. Show us your work and we can guide you from there.

3. ### WBahn Moderator

Mar 31, 2012
20,215
5,744

Also, if you want people to open an attached image file, you might want to take a few minutes to make the size reasonable. Instead of 5MB, you should probably be looking for something more along the lines of 50 KB. Try something as simple as using Paint and resizing the diagram to be about 300 pixels wide instead of whatever it is now.

Finally, you are expected to show YOUR best attempt to solve YOUR homework problem.

4. ### gonzasvydd Thread Starter New Member

Nov 30, 2014
4
0
I understand that but the only thing I was able to come up is that R3 and R4 have 0 current going through. From there I am stuck.

5. ### WBahn Moderator

Mar 31, 2012
20,215
5,744
So, again, what is your question? Are you expecting someone to just work your homework for you? If not, what ARE you expecting? Your thread title says you have an op-amp circuit question, but you have yet to ask any question at all.

What are the consequences of having no current in R3 and R4? Are there any nodes for which you CAN determine the voltage for? What nodes will end up having the same voltages as a consequence of the op-amp operating in its active regime?

6. ### gonzasvydd Thread Starter New Member

Nov 30, 2014
4
0
The question is to find the voltage of the output. I am not expecting you to solve the question I just need some guidance as to where to go about solving the problem.

this is what I have so far:

part A:
i1=(Vs1-Va)/R1
i2=(Va)/R2

part B:
i6=(Vo-Vb)/R6
i5=(Vb-Vs2)/R5

i3=0
i4=0

7. ### WBahn Moderator

Mar 31, 2012
20,215
5,744
So if the question is to find the voltage of the output and you are not expecting us to solve the question, then that clearly can't be the question you have for US. Finding the voltage at the output is your homework's question for YOU. What you need to do is figure out what question YOU want to ask of US. I know that this can be a strain, but it also forces you to think about the problem in a more focused way in order to come up with specific questions about the problem that, given an answer (or, preferably, confirmation on your thoughts regarding those questions) will help move you in the right direction.

What isn't very helpful is to throw out a bunch of ill-defined equations. You say that you have I1 = (Vs1-Va)/R1. What is Va? What is I1? We are not mind readers! Define your variables and your terms. If you talk about I1, then it better be defined what, exactly, current I1 is which means what path it flows through and in what direction. If you talk about the voltage at a point, such as I'm assuming Va is, then you need to define what node that voltage is associated with. If you talk about the voltage across some component, such as a resistor, you need to define what component (or what the two points that the voltage is taken across) and what the polarity of that voltage is.

If you will take the time to clearly define your variables in the above equations, preferably with an annotated diagram that is less than 100 KB in size, then I believe I can ask you some questions about those equations that will help move you in the right direction.

Feb 19, 2010
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Apr 26, 2005
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here it is

File size:
4 KB
Views:
42
10. ### WBahn Moderator

Mar 31, 2012
20,215
5,744
I was hoping to get the OP to step up and post a better pic, which he still needs to do since his terms are undefined. When I just took his original diagram and resized it in Paint to 300 pixels wide it reduced it to 30KB.

11. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,673
1,536
I'd be surprised if he returns ...

12. ### WBahn Moderator

Mar 31, 2012
20,215
5,744
He might -- he was showing some attempts at what he did, which is so much more than many.