Electronics > Projects, Designs, and Technical Stuff
lab standard clock buffer module.
tkamiya:
I am designing a sort of "fan out" board for various timing frequency sources - the kind that keeps lab full of gear in sync. I am finding out there is no agreed upon values and levels on these things, so I'm trying to accommodate most of situations. First in order is a unit that plugs directly into the frequency source to bring the output to usable level AND protect the source from reverse input.
For example, PRS-10 puts out 10MHz, 0.5Vrms, 1.41Vpp, and +7dbm (50ohm)
HP8644 expects 0.5Vrms (7dbm) to 2Vrms (19dbm)
Account for loss and mismatches, it seems prudent to provide 15db or so amplification, adjustable to 0db. That would probably mean using OP amp.
There are plenty of video amp that seem appropriate for this kind of use but problem is, almost all of them are surface mount. I would very much like to avoid this. So I'm looking for 8 pin can or DIP packaging. In addition to compensating for loss, I plan to use an attenuation and transformer to further isolate/protect the source. So minimum 20db of gain is necessary.
Given these parameters, can anyone give me a recommendation? This really isn't a distribution amplifier but sort of a buffer. So I don't mind spending few dollars on it. For distribution amps, I already have symmetricon set up.
David Hess:
Good devices should be intolerant of signal levels but many are not. The most universal simple solution is to provide TTL levels at the receiver so low is below 0.8 volts and high is above 2.0 volts which can be satisfied by a 5 volt CMOS double terminated output without exceeding 5 volts. More sophisticated solutions can provide a full 0 to 5 volts from a 5 volt supply with proper double termination without exceeding 5 volts if the load termination is missing by using a linear driver and positive feedback but this is probably unnecessary.
tkamiya:
Many of my equipment specifies sine wave though....
awallin:
I tried to collect a few links on this page, for design inspiration:
https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/similar-projects
if you find open designs and/or measurements that are not listed on that page - please post here! thanks.
LapTop006:
For some very similar use cases I've been playing with the Linear Tech LTC6957 as the frontend.
My case is fixed frequency (just 10MHz) so I then just use standard gates to buffer (74S120 if you're driving 50-ohm loads), and LC filters to get it back to a sine.
You might also want to look at the Spectracom 8140 system which may be useful as an existing solution available cheaply used.
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