Attenuator calculation or formula

Discussion in 'General Electronics Chat' started by PickyBiker, Mar 19, 2016.

  1. PickyBiker

    Thread Starter Member

    Aug 18, 2015
    56
    1
    I have a microprocessor that is putting out 3.4V pulses and it needs to drive a sensor with a max input voltage of 2.4V

    I think a T attenuator would work, but I don't know to calculate the values. Anyone got a calculator that works with voltage instead of db? A simple formula would be alright too.
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,127
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    There are more than one way to do this, but I might just use a resistive divider. What does the sensor require in terms of current, mA?

    Another way could be as simple as putting 2 diodes in series with the signal. Together they will drop ~1.2-1.4V.
     
  3. #12

    Expert

    Nov 30, 2010
    16,298
    6,811
    You don't need a T-attenuator. This is the basic shape of it considering I have no idea how much current the load needs.
    Vo = Vin R2/(R1+R2)
     
  4. PickyBiker

    Thread Starter Member

    Aug 18, 2015
    56
    1
    The current required to raise/lower the sensor input is 10ua.
     
  5. #12

    Expert

    Nov 30, 2010
    16,298
    6,811
  6. wayneh

    Expert

    Sep 9, 2010
    12,127
    3,048
    In that case, a resistive divider as I and #12 mentioned, and which #12 illustrated, would be fine. The 10µA load of the sensor would introduce only a small error (~1% max) in the 1mA flowing through the resistors. That error is likely dwarfed by other sources of experimental error.
     
  7. PickyBiker

    Thread Starter Member

    Aug 18, 2015
    56
    1
    Thank you guys!!!
     
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