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Art of Electronics Exercise 4.3 Operational inverter

  1. Mar 20, 2013 #1
    1. The problem statement, all variables and given/known data
    The circuits in Figure 4.14 let you invert or amplify without inversion, by flipping a switch. The voltage gain is either +1 or -1, depending on the switch position.
    http://tinypic.com/r/2hnql2c/6
    http://tinypic.com/r/2hnql2c/6

    2. Relevant equations
    Gain for the first image with the switch set to ground is equal to -R2/R1, because it is an inverting amplifier, struggling to identify how to consider the circuit as a follower, because it doesn't look like a typical follower circuit. Unsure how to consider the circuit when the positive and negative terminals are connected.


    3. The attempt at a solution
     
    Last edited: Mar 20, 2013
  2. jcsd
  3. Mar 20, 2013 #2

    berkeman

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    Staff: Mentor

    What is the difference in voltage between the + and - inputs for an opamp in the follower configuration? So what is the feedback current in this configuration? :smile:
     
  4. Mar 20, 2013 #3
    are the + and - inputs equal, because of the negative feedback loop?
     
  5. Mar 20, 2013 #4
    so the voltage across the 1st resistor would be 0V because it is V+ - V-
     
  6. Mar 20, 2013 #5

    berkeman

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    Staff: Mentor

    Correct-a-mundo :smile:

    Kind of a wierd follower, but that's one of the ways that H&H teaches us how to be comfortable thinking about circuits. Have you seen this thread?

    https://www.physicsforums.com/newreply.php?do=newreply&p=4315656 [Broken]

    :smile:
     
    Last edited by a moderator: May 6, 2017
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