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average voltage

Discussion in 'General Electronics Chat' started by ARUNA711, Mar 7, 2007.

  1. ARUNA711

    Thread Starter New Member

    Mar 7, 2007
    HI ,

    I just have a doubt in the third chapter of our e-book - operational amplifiers-averager and summer circuit.The formula to get voltage is E=IR.In this chapter to find the average voltage the formula is different.

    Please advice me

    P Arunachalam
  2. Papabravo


    Feb 24, 2006
    Can you provide a link to the e-book or elaborate a bit by telling us how it is different?
  3. Dave

    Retired Moderator

    Nov 17, 2003
    I assume this is the section in the e-book which you having issues with?

    The maths seems in order to me, which bit are you refering to?

  4. thingmaker3

    Retired Moderator

    May 16, 2005
    Looks like Ohm's Law to me...

    "The voltage at the virtual ground is now held at 0 volts by the op-amp's negative feedback, whereas before it was free to float to the average value of V1, V2, and V3. However, with all resistor values equal to each other, the currents through each of the three resistors will be proportional to their respective input voltages. Since those three currents will add at the virtual ground node, the algebraic sum of those currents through the feedback resistor will produce a voltage at Vout equal to V1 + V2 + V3, except with reversed polarity."
  5. ARUNA711

    Thread Starter New Member

    Mar 7, 2007
    Thanks for your reply. Since I am a bigginner I coudn't catch that formula.
    Now I am clear.
    Thanks a lot.