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LMH6702: LMH6702

Ao Sun
Intellectual 1670 points
Part Number: LMH6702

lmh6702.docx

  • 0
    Guru 140200 points

    Hi Ao,

    the gain determining resistors of the feedback loop of LMH6702 must be mounted closest to the OPAmp. In your case the distance is way too long:

    Kai

  • 0 in reply to kai klaas69
    TI__Intellectual 1670 points

    The data sheet repeatedly emphasizes the size of the load impedance, 100 ohms, 50 ohms, etc., can the sch  I use adapt to the use of different loads?

  • 0 in reply to Ao Sun
    Guru 140200 points

    Hi Ao,

    I'm sorry, I don't fully understand your question.

    But if you think you can solve the instability by the choose of a certain load resistance, then I'm afraid to say that the instability can only be cured by a redesign of the layout of LMH6702.

    Hey, the LMH6702 is a 1.7GHz OPAmpRelaxed 1.7GHz is 1700MHz! With such a HF OPAmp every millimeter of copper tracks count. And the green circled copper track is way way way too long.

    Kai

  • 0 in reply to kai klaas69
    TI__Intellectual 1670 points

    What is the carrying capacity of this circuit? Will instability occur under different loads?

  • 0 in reply to Ao Sun
    TI__Genius 17306 points

    Hello Ao,

    Stability can be affected by a selected load; are you asking for particular guidance on understanding how to use LMH6702, or do you have specific loads or 'carrying capacities' which you are concerned about?

    When designing your circuitry, the LMH6702 circuit will depend on the size, type, and other parameters of the load you are driving.  You can design a circuit which accommodates various loads, but the performance may not be as good as if you designed for a single load value.

    Kai's advice on your layout is also important; your design will be affected by unnecessarily long traces and other PCB layout decisions.

    Best,

    Alec