how to amplify the output of light sensor using op amp?

Discussion in 'The Projects Forum' started by hvc123, Aug 2, 2012.

  1. hvc123

    Thread Starter New Member

    Aug 2, 2012
    i got the output of photodiode about 0.5v... how can i amplify it?
  2. hvc123

    Thread Starter New Member

    Aug 2, 2012
    i am going to make electronic spirometer... i will use led and photodiode... in between them there is a fan which rotates when we blow in that chamber... when the flaps of fan will cut the light which falls on the photodiode, the output will zero... and when it not cut the light it will give some voltage of 0.5v.. pls give me idea about this logic... i am not sure it will be work or not .... . . :-(
  3. #12


    Nov 30, 2010
    [​IMG]This is an op-amp circuit that I copied from the "Worksheets" section on the top of the "Projects" page. The formula for gain is: input voltage times 1+R1/R2. You only need to give the amplifier some voltage to work with and decide how much amplification you want. Tell us more if you want more help.
    hvc123 likes this.
  4. hvc123

    Thread Starter New Member

    Aug 2, 2012
    bt now i need to know about electronic spirometer.... pls give me idea
  5. wayneh


    Sep 9, 2010
    You opened the thread asking how to amplify a small signal. Answered.

    Now you're asking about a spirometer. Is there a question?
  6. DickCappels


    Aug 21, 2008
    My recommendation is to operate the diode in the photocurrent mode because it will be more linear. If you operate it in the photovoltaic mode (open circuit), you will find that its output starts getting compressed as it approaches 0.5 volts very early on. If you aren't using a long cable, you can dispense with the 22 uf capacitor and get a frequency response mostly limited by the capacitance of the photo diode, the characteristics of the opamp and the feedback resistor. You can actually take this basic circuit up to the hundreds of MHz, but that would be a whole different discussion.

  7. ramancini8

    Active Member

    Jul 18, 2012
    How do you get a TLC27L2 to operate at hundreds of MHz?