1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Operational amplifier with feedback problem

  1. Nov 23, 2016 #1
    1. The problem statement, all variables and given/known data
    upload_2016-11-23_22-8-8.png

    2. Relevant equations


    3. The attempt at a solution
    IMG_20161123_220433.jpg

    Using the equations above, I'm not getting the right answer for beta which is 0.4926 V/A.
    Is my model wrong ?
     
  2. jcsd
  3. Nov 24, 2016 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    The op-amp's ro should be shown in series with the controlled voltage source.
     
  4. Nov 25, 2016 #3
    So with a voltage source, ro is always in series ?
     
  5. Nov 25, 2016 #4

    NascentOxygen

    User Avatar

    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?
     
  6. Nov 25, 2016 #5
    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
     
  7. Nov 25, 2016 #6

    NascentOxygen

    User Avatar

    Staff: Mentor

    Guessing is not allowed.

    Can you determine it?
     
  8. Nov 25, 2016 #7
    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
     
  9. Nov 25, 2016 #8

    NascentOxygen

    User Avatar

    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.
     
  10. Nov 25, 2016 #9
    Ok, thanks, I'll attempt the question again
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Operational amplifier with feedback problem
Loading...