Tl431

Discussion in 'General Electronics Chat' started by firend, Aug 14, 2013.

  1. firend

    Thread Starter Member

    Feb 18, 2012
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    Hello all!
    Can anyone help me?
    I have a question. when TL431 uses as a op-amp with reference voltage 2.5 to generate compensator type 2. why is mininum catode -anode voltage 2.5V?
    thanks in advance!
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    745
    you set the voltage using two resistors on the gate pin


    datasheet
     
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  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Have you looked at the datasheet? 2.5V is the reference voltage. As Dodgydave pointed out, you can make the cathode voltage higher with a voltage divider. See Fig. 20.
    Dave incorrectly called the feedback pin "gate". It is actually the "ref" pin.
    See the attached specs.
     
    Last edited: Aug 14, 2013
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  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    In SMPS we use TL431 as a error amplifier. The mininum catode-anode voltage is reach when TL431 is full ON (saturated). This voltage is in range between 1.8V ... 2.2V region. But in calculation we use 2.5V as worst case scenario.
     
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  5. firend

    Thread Starter Member

    Feb 18, 2012
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    Thank you for replying!
    I wonder if catode-anode voltage can be under 2.5V. its value is output of error amplifier. I want to it as error amplifier.
     
  6. firend

    Thread Starter Member

    Feb 18, 2012
    44
    0
    Thank you.
    It is true. its value is about 2V. I want to use to generate VAK when Vo changes.but VAK has only 2 values. it is 2V or the one Vo.
    I attach circuit in file.
     
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