# solve OP amp with node analysis

Discussion in 'Homework Help' started by chrill3123, Apr 21, 2010.

1. ### chrill3123 Thread Starter New Member

Apr 21, 2010
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0
I have a problem regarding homework, its about nodeanalysis in a circuit involving OP amp, I dont really understand how to deal with the OP amp part...

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2. ### The Electrician AAC Fanatic!

Oct 9, 2007
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Start out by writing KCL equations for nodes 2 and 5. Let the voltages at your nodes be V1 at node 1, V2 at node 2, etc.

The equation at node would be:

(V2-V1)/2000 + (V2-V3)/3000 = 0

Later, you can set V1 = 1 volt and V3 = 2 volts.

Try you hand at writing an equation for node 5.

3. ### chrill3123 Thread Starter New Member

Apr 21, 2010
9
0
I dont understand how calculate with the ideal OP amp, it should be infinite impedance from output and zero impedance from input i think, but in calculations how do it be?

4. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,300
335
The infinite impedance at the inputs means you don't have to allow for any current into those terminals.

Look at the equation I gave you in post #2; there is no term for current into the opamp inputs.

Just write a similar equation for node 5. Do you know how to use the nodal method of circuit analysis?

You need 3 equations in 3 unknowns. Your unknowns are V3, V4 and V5. V1 and V3 are known.

Your 3rd equation will be: V2 = V5.

So, try to write an equation for node 5.

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