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LM7171 in Howland current source

rahman yunus
Prodigy 130 points
Other Parts Discussed in Thread: LM7171

Hi,

I am testing a fabricated circuit using LM7171 in Howland current source circuit to supply 10mA in frequency range between 10kHz to 500kHz. I find that during operation the IC at the unity gain buffer (U4) is running hot. Is this indicates that the IC not unity gain stable? or any other reasons for the problems? If the device is not unity gain stable any suggestions for other amplifiers which has stable unity gain? Please advice.

Regards

Thank you

  • 0
    TI__Mastermind 22825 points

    Hello,

    If you are suspecting that U4 might be oscillating, may be you can try and changes its close loop gain (by installing RF and RG) to +2V/V to see if its case temperature goes back to normal.

    Is it possible for you to try the above as an experiment at first?

    The LM7171 is unity gain stable, but it could have some peaking especially if there is parasitic capacitance involved.

    Regards,

    Hooman