offset problem of AD8629 OPAMP

Dear Sir/Madam,

Our customer have met one trouble as following.

(This discuss came from another sled cause my miss understood)

On my enclosed schematic Fig-1.pdf,

step-1 power off and keep waiting around 30 sec

step-2 power on

step-3 around 90msec offset voltage appear at out-1 pin

step-4 power off and on but the 90mV offset is not cleared

Also refer to my enclosed time chart "tme chart when power off and on.pdf".

note

*1 ; 30sec is not certainly.

*3 ; in some cases, it return to expected value

After once this trouble happen, out-2 is up and dowm on offset voltage 900mV(x10 gained value)

 

When we work with above action, does your AD8629 do such a motion?or not.

If he replace the thermopile(TP) to fixed resister 175kohm, then the result was same.

Please advice us before your holiday!!

Thank you in advance Kaos

attachments.zip
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  • Hi Kaos,


    Apologies for the delay of response. You mentioned that in the circuit you gave, the TP was replaced by a 175k fixed resistor but how about the 5V and resistor divider connected on the inverting input, is it still present when the customer is testing the circuit? With the current configuration, any voltage between 10k and 910 resistors will be reflected on the output with a gain of 1 as previously mentioned on the older thread. It would be helpful if you could provide the updated circuit that the customer is using.


    Thanks.


    Chard

Reply
  • Hi Kaos,


    Apologies for the delay of response. You mentioned that in the circuit you gave, the TP was replaced by a 175k fixed resistor but how about the 5V and resistor divider connected on the inverting input, is it still present when the customer is testing the circuit? With the current configuration, any voltage between 10k and 910 resistors will be reflected on the output with a gain of 1 as previously mentioned on the older thread. It would be helpful if you could provide the updated circuit that the customer is using.


    Thanks.


    Chard

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