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PCB for high speed amplifier

witat rangtain
Prodigy 60 points
Other Parts Discussed in Thread: DEM-OPA-SO-1A

Hello TI engineers

     I saw PCB for high speed amplifier DEM-OPA-SO-1A like a picture and I have 2 questions about this design.

1. Why top side has no ground plane?

2. Why ground plane at bottom side blank area IC ?

Best regards

Witat

  • 0
    TI__Genius 13935 points

    Hello Witat,

    I can't answer for the missing ground plane on the top layer, but the cut out from under the amplifier is to reduce parasitic capacitance on the I/O pins.  The inverting input and the output pins are both sensitive to parasitic capacitance.  This is explained on page 5 of the datasheet. 

    This looks like an older design.  We don't use many through hole SMA connectors anymore.  Edge mounted connectors provide a better impedance match. 

    Loren