Differential Amplifier Design Question

Discussion in 'Homework Help' started by jegues, Jan 30, 2011.

  1. jegues

    Thread Starter Well-Known Member

    Sep 13, 2010
    Hello all,

    I've been working on the following question (See figure attached).

    I'm on part (ii) and the solution gives this circuit (See other figure attached) as the one that will provide a gain of +2V/V.

    I'm tried doing some analysis on the circuit to figure out whether this is right or not but I can't conclude that it indeed gives a gain of 2V/V.

    What am I doing wrong?

    I've got a feeling my calculation for V_{+} is wrong.

    Can someone clarify?
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    In your diagram, V+ = Vin
    So the gain is equal Av = 1+ R/R = 2V/V
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    The point to note is that the two resistors connected to the non-inverting input are in parallel. They do not form a potential divider in this example.

    Perhaps you thought one of these resistors was connected to ground, having seen similar arrangements where this was the case? Circuits need to be read carefully.