TL 072 op amps

[barry wilkins]

I have been making a circuit using a couple of these op amps.
On some of these pin 2 voltage is about 3 millivolts different to pin 3.
A few of are very poor ,could be faulty ?
It does not to seem to be too much of a problem the output of the differential amplifier seems to zero.
.Does any one know why.

Barry

[mscottdoran@gmail.com]

Can you post a schematic of the circuit you are using it in? Maybe it's just due to the precision limits of the meter you are using to take the measurement? Depending on the circuit and due to the inherent high gain of those op amps, if the output is zeroing it seems like the op amp isn't “seeing” any voltage difference between the inverting and non-inverting inputs.

[stj]

2 & 3 are inputs,
your supposed to supply voltage not meter parasitic leakage etc.
if you look at page 26 of the datasheet you will see they are not identical internally anyway

[redwire]

It's normal to see 3mV difference; Input Offset Voltage V_IO spec is 3-10mV for the TL072.