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TL074: temperature drift related to the load resistance

Howard Zou
Genius 12365 points
Part Number: TL074


Hi,

My customer is using TL074 to measure 230V AC voltage. When the temperature rise from 20C to 80C, the voltage measurement result they got deviate about 10V.

Then they tried decrease RC10 and RC16 from 20k to 1k, the deviation is just 5V.

Why would this happen? Are there any inappropriate point in the schematic below?

  • 0
    Guru 140200 points
    Hi Howard,

    hard to say without knowing the input signals. So, what are the input signals? And do you have scope plots?

    Kai
  • 0 in reply to kai klaas69
    TI__Guru**** 167546 points
    Howard,

    Based on this experiment "Then they tried decrease RC10 and RC16 from 20k to 1k, the deviation is just 5V.", I suspect that impedance at M-Grid and R-grid changes with temperature. Does the output at pin 1 also vary?

    What is the desired output in mathematical terms based on the input difference voltage? The common mode range for the input signal is also needed to verify that the op amp input common mode range is correct.