Calulating the gain

Discussion in 'General Electronics Chat' started by dmanzay, Oct 27, 2011.

  1. dmanzay

    Thread Starter New Member

    Oct 25, 2011
    5
    0
    Can someone tell me if this is right, If Rf = 10k ohms and Ri =100 ohms would the gain be a -10, if the signal is 1V and the input frequency is 100 Khz, would the output voltage be -1.10v. I'm trying to find out if I'm right.

    Dmanzay
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    Are you talking about an inverting op amp connection? If so then the gain is -Rf/Ri, which is not -10.

    The frequency has little effect on the output voltage until you reach the gain-bandwidth limit of the op amp. If below that frequency then the output would be equal to the input voltage times the gain.
     
    dmanzay likes this.
  3. dmanzay

    Thread Starter New Member

    Oct 25, 2011
    5
    0
    Yes it's a inverting Op-amp, so would the gain be Gain = 1+(-Rf/RI), if so that would give me 1.10v am I right.

    Dmanzay
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    No. The gain for an inverter is as I previously stated. The factor of 1 is used for the gain of a non-inverting op amp (without the minus in front of Rf/RI).

    You math is way off. How do you get a gain of 10 and an output of 1.10v by multiplying -Rf/RI * 1V?
     
  5. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
    26
    Hint: Change 10k to 10000

    --Rich
     
Loading...