There are a lot of buffers that can be used for this kind of application.
Charles, you did not specify the format that you need after you picked off
the clock data. I'll recommend a couple different parts. The first has a
pair of PECL outputs, the ON Semi NB6L11. It has a universal differential
input and can operate off either 2.5 or 3.3Vcc. There is also an ON Semi
NB6L11S that has a pair of LVDS drivers outputs and operates at 2.5V.
Tom Dagostino
971-279-5325
tom@xxxxxxxxxxxxxxxxx
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Dave Cuthbert
Sent: Saturday, February 13, 2016 2:26 PM
To: Charles.Grasso@xxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Measuring HF signals with no corruption.
A voltage op amp has an input capacitance of 3 pF which will load your 500
ps risetime signal with about 170 ohms. A less intrusive way to pick off the
signal is through a resistive divider of 451 ohm and 50 ohms. The loading is
then a rather light 500 ohms. If the 10:1 divider ratio is too great for you
functional check circuit it can be amplified.
A 10X amplifier can be built with the Linear Technology LTC6409 Op Amp. Its
GBP is 10 GHz. The Op Amp input resistors are the 50 ohm divider resistors
and so the Op Amp and 50 ohm resistors can be off the board and fed via two
50 ohm coaxial cables or 100 ohm twisted pair. LTSpice has this Op Amp and I
would simulate it. If you don't do LTSpice I will run it for you.
Dave Cuthbert
On Fri, Feb 12, 2016 at 1:45 PM, Grasso, Charles <
Charles.Grasso@xxxxxxxxxxxx> wrote:
Hello,
We need to use a high speed clock from our mother board to enable a
functional check circuit. One of the obvious constraints is that the
signal "tap" is not permitted to change the signal in any way.
One solution would be to use opamps (which have a high z input)
however I cannot seem to find a solution that is fast enough. (The
signal is LVDS based and the spec says the 20-80 rise time min is
500ps running at 200MHz)
My initial thought is that I would need a gain/bw product of around 1GHz.
Does this august body agree?
That being the case - would someone be so kind as to point me at a
part that might work?
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications
(w) 303-706-5467
(c) 303-204-2974
(t) 3032042974@xxxxxxxxx<mailto:3032042974@xxxxxxxxx>
(e) charles.grasso@xxxxxxxxxxxx<mailto:charles.grasso@xxxxxxxxxxxx>
(e2) chasgrasso@xxxxxxxxx<mailto:chasgrasso@xxxxxxxxx>
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