I was test a board containing LMC6462AIM as high impedance buffer, +ve pin to 1K to 0V (for test), wire link between -ve to output (gain=1V/V). Output load 100K. The power is +/-5V from linear bench PSU. The room temp is 25C and the PCB is very clean, no residual flux or dirts.
Now using precision DVM, I measure 0.0mV at the +ve pin. I then measure the output and found to be -2.1mV.
According to the datasheet the maximum offset should be 1.2mV and typical being 0.6mV, which is why I choose this device. I was surprised to measure this. I tried different DVM and the result is the same, the voltage offset exceed the manufacture.
I tried other op-amp within the same batch and it has similar results. It must be bad batch but it leave me wonder how they occurs, why National fails to rejects them and how to avoid this happening again.