ISO224: Maximum Input Resistance

Hi Ray,

Ray Vincent Aranzaso said:

It is because the ideal input resistance of an op-amp is infinite?

No, this is not the reason. Usually, it is the minimum input resistance which can become an issue, since the input resistance forms a voltage divider in combination with the source resistance of the circuit driving the input of ISO224. To find out the worst case error caused by this voltage division, the minimum input resistance needs to be known. And since each min and max specification in the datasheet makes a costly and time consuming factory check necessary, the number of these specifications is limited to absolute necessary.

I guess that the max specification of input resistance is about 25...30% above the typical value.

Kai