FreeLists / si-list / [SI-LIST] Re: Measuring high speed signals

["S. Weir" <weirsp@xxxxxxxxxx>]

Alex,  this is a simple decoupling exercise.  The test port loads your 
signal with a relatively high impedance, while the scope port sees a low 
impedance, and smaller signal, sic resistor divider, large resistor to the 
test signal in series with a small resistor across the test port.  The 
attenuation ratio sets the relative decoupling.

Regards,

Steve.
At 10:00 AM 6/11/01 -0700, you wrote:

>I'm looking for some techniques for probing differential signals 1 Gig and
>above. I could use a differential probe but the one I have has no easy way
>to connect to the board other than physically holding it which is not
>acceptable. On the other hand I could use 50 Ohm coax with a SMA connection
>except then the scope circuit becomes part of the PCB circuit. In some of
>the papers at teradyne.com, they say they use an SMA connection in
>conjunction with resistors to provide some isolation. Anyone have any
>suggestions or know what circuit they are using to provide isolation?
>
>
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