Input impedance of ICL7107

Thread Starter

Rogare

Joined Mar 9, 2012
78
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.)
 

Audioguru

Joined Dec 20, 2007
11,249
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.
 
Top