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LMP7702 Temperature sensitive amp

Other Parts Discussed in Thread: LMP7702

Dear Comminity,


I have a probelm with one of my 2 opamp inside the LMP7702. The opamp is super-sensitive to temperature: when below 40 deg everithing is fine but when the temperature gose over 40 deg, I found the output be saturatet to the rail voltage. Consider that the other opamp in the pakage is working fine also with the temperature change.


That's my circuit

The opamp in the U506 is satuarting with the incresaing of temperature and the others that are close togherter works fine. Also the 4 DAC are working fine. In additio the risistors are all 0.1%

What happens? Can you give me an hint?

Best,

CM4

  • Hi Mario,

    If you replace U506 with another "fresh" unit, does it still behave the same? What is the DAC output voltage? How much difference in the output between the "good" channels and the "bad" channels?

    Is it just one channel of U506, or both?

    Is there a particular reason you are attenuating (R504/508) and then gaining-up the signal? You have a signal gain of 1, but a noise gain of 3.3 - which will amplify any amplifier errors by 3x.

    Are there any cuts or jumpers or other rework in the circuit that is not shown in the schematic?

    Have you checked for oscillations on the output of U506? Is the load capacitive? (>100pF) It looks like U506 and U507 are driving different loads.

    Regards,