# Operational amplifier with feedback problem

1. Nov 23, 2016

### TheRedDevil18

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Using the equations above, I'm not getting the right answer for beta which is 0.4926 V/A.
Is my model wrong ?

2. Nov 24, 2016

### Staff: Mentor

The op-amp's ro should be shown in series with the controlled voltage source.

3. Nov 25, 2016

### TheRedDevil18

So with a voltage source, ro is always in series ?

4. Nov 25, 2016

### Staff: Mentor

Yes.

If you were to place a resistance in parallel with an ideal voltage source, what would be the Thévenin equivalent resistance of that combination?

5. Nov 25, 2016

### TheRedDevil18

Would it be a voltage source in series with the resistance ?, I know that a current source with a parallel resistance is equal to a voltage source in series with that resistance

6. Nov 25, 2016

### Staff: Mentor

Guessing is not allowed.

Can you determine it?

7. Nov 25, 2016

### TheRedDevil18

Would it be zero ?, I determined it by using the rules. When you have a voltage source you short it and remove the load, so that means all the current will flow through the short and not through the parallel resistor

8. Nov 25, 2016

### Staff: Mentor

Right. A resistance has no effect if you erroneously add it parallel to an ideal voltage source: the effective source resistance here would stay as zero.

9. Nov 25, 2016

### TheRedDevil18

Ok, thanks, I'll attempt the question again