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Input impedance of ICL7107

Discussion in 'General Electronics Chat' started by Rogare, Apr 12, 2012.

  1. Rogare

    Thread Starter Member

    Mar 9, 2012
    78
    0
    Does anyone know the input impedance of the ICL7107 chip using the standard setup in Figure 2 (page 4)? There's a 1MΩ resistor in series with one of the differential inputs, but not sure how to model this...

    (I can't seem to find it on the spec sheet and I haven't found a good source for this online.)
     
  2. Audioguru

    Expert

    Dec 20, 2007
    11,251
    1,350
    The chip is Cmos. Then its input resistance is infinite. It has no input current, just a very tiny leakage current.

    The 1M series input resistor reduces current to the input protection parts when the input voltage is too high. The 1M resitor is also part of a lowpass filter with the input capacitor.
     
    Rogare likes this.
  3. Rogare

    Thread Starter Member

    Mar 9, 2012
    78
    0
    Thanks for the explanation!
     
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