AD8009 Heating up

Hi

I am using a AD8009 OPAMP along with AD834 DDS based circuit with -4.4V to +4.4V supply, at these case AD8009 is extremely heating up and it is giving output as well, what causes to heating up the AD8009 ? 

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  • Hi navtech,

    Please, tell us the current consumption and the actual temperature of the case. Information about the output load and the type of signal can also be useful.

    Regards,

    Kirill

  •   Thanks for replying , positive rail is consuming 60.4mA and negative rails is consuming 8.6mA currents. type of signal is sine wave and temperature of IC is rising up to 80 degrees   

  • Since the current consumption is asymmetric, I conclude that the output voltage of the amplifier is pulled up to the positive rail and remains so. I'm right?

    Tell us more about the circuit. The amplifier doesn't have local feedback, do you want to get non-linear operation mode? Or is there another loop? W1 and W2 refer to a other multiplier that is not shown here?

  • We are expecting non linear operation mode only, there is no other loop on this circuit, In data sheet the power supply of AD8009 is mentioned a 5v to +/-5v operation, In this case circuit is working with a +/-4.4 voltage configuration.  

  • The current feedback amplifier does not have a differential pair at the input and its inputs are fundamentally different. Unlike a classic amplifier (and comparator), it reacts more to the difference in input currents rather than potentials. Theoretically, it can work as a comparator, but you need to keep these features in mind. Have you previously used current feedback amplifiers in this role and are you sure it should work?

    First of all, I would check that the amplifier is working properly and that its behavior is adequate in this mode. If possible, disconnect the wires W1 W2 from the rest of the circuit and apply different voltages to them within the power rail, check the behavior of the amplifier output. Please tell us about the results.

    Regards,

    Kirill

  • We never had any experience in using current feedback opamp but we are pretty much confident in said configuration.

    • node W1 and W2 are current DAC output of AD834.
    • We have got proper simulation output from LTSPICE without any convergence issue.
    • This configuration is entirely a reference circuit on AD834 datasheet.

    We will do the testing as you recommended and will get back to you soon.     

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  • We never had any experience in using current feedback opamp but we are pretty much confident in said configuration.

    • node W1 and W2 are current DAC output of AD834.
    • We have got proper simulation output from LTSPICE without any convergence issue.
    • This configuration is entirely a reference circuit on AD834 datasheet.

    We will do the testing as you recommended and will get back to you soon.     

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