My customer would like to design TLV1805 and need to know the value of input impedance for TLV1805.
We can't find it from datasheet. Please check.
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For CMOS opamps, the input bias current is caused mainly by leakage through the ESD protection diodes. The behaviour is not really the same as for a plain resistor (see figures 9…12 in the datasheet).
In most applications, the input bias current specification is enough to design the circuit. If you really want an impedance value, use Ohm's law (R = VCC / IB).
Unfortunately, the TLV1805 datasheet does not give a worst-case value.
specifiying an input resistance makes only sense when the "input voltage to input bias current curve" follows the Ohm's law. But figures 10, 11 and 12 of datasheet demonstrate that this not the case for the TLV1805. The input bias current flowing in and out of the inputs of TLV1805 is more a leakage current and is not caused by an ohmic resistance. Because of that the datasheet only contains information about the input bias current.
The customer should determine the maximum ambient temperatur (or chip temperatur) in which the TLV1805 is operating in his application and should determine by the help of figuires 9...12 whether his circuit will work well with the expected input bias currents.
Keep in mind that the curves are only showing typical performances. If he needs guaranteed maximum values he should look for another comparator.