1. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    opamp.JPG in fig 1 we see that there are 2 diodes between the 2 input ,and these for protect the input of OPAMP so it will never the difference between 2 input be more than .7v ,my question is why we connect no inverting input to 10k to ground and not connected direct to ground?
    and also in the second OPAMP we connect the 2 diodes after 47k? so why this
    and in fig 2 we connect 200k parallel with .01uf ,so is this low pass filter and how can I chose the value of 200k and .01uf
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,134
    268
    It would be helpful if you would provide more information about what you are building? it's not at all clear from the schematic.
     
  3. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    this is control board for power supply
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,813
    1,105
    If the inverting and non-inverting inputs of the opamp have similar resistance paths for DC bias current the effect of DC offset drift will be reduced.
     
  5. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    can you explain more please
     
  6. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    Can you read more?

    You've been told that it is to minimize the effect of DC offset drift related to the DC bias currents. So go look into the effects of DC bias currents in opamps.
     
  7. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    Thanks so much ,you are right
     
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