Attila wrote:
I am currently looking at the LT1677/1678/1679 family of opamps, which
have an increadibly low tempco for the input offset voltage (0.4µV/°C typ).
* * *
But, when the input voltage comes close within the upper or lower rail,
the input offset voltage specs get much worse. * * *
is my assumption correct, that with worse offset spec, close to the
rails, also the offset voltage drift specs get worse?
That is almost certainly true, but it is not specified by the
manufacturer. You would have to test for yourself to know for sure.
Note that, in addition to the offset voltage changes, the input current
and input offset currents also change with the common-mode voltage.
Both are due to the rail-to-rail *input* architecture, and are common to
RRI opamps.
Compare this to the AD8675, which is RRO but not RRI. Its input offset
tempco (typical) is even better than the LT1677 (0.2uV/C), as well as
its input noise (2.8nV/sqrtHz with a very low 5Hz 1/f corner frequency),
but without the input common mode effects of the 1677.
If RRI is important in your application, you may be able to do without
an actual RRI opamp by running the opamp on higher supply voltages than
the rest of the circuit.
Best regards,
Charles
_______________________________________________
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
