[time-nuts] HP 5087A Input Doubler and 10 MHz Ampifiers
bruce.griffiths at xtra.co.nz
Tue Jul 8 00:39:44 EDT 2008
John Miles wrote:
> There is nothing special about the 5087A's amplifier cards. The 5087A
> design is not especially quiet; in fact, it will degrade the broadband floor
> of a Thunderbolt by a good 7 or 8 dB from what I have seen.
> I'd say grab some PCB prototyping stock and a Dremel tool, and surf through
> Bruce's notes and references at
> http://www.ko4bb.com/~bruce/IsolationAmplifiers.html for some ideas.
> -- john, KE5FX
Just watch for the odd error in those references.
eg in the first reference (.../498.pdf) the captions for figure 2 and
figure 3 should be swapped.
If anyone wants to try it, I have an even quieter, lower distortion 3
transistor isolation amplifier design that runs from a 12V supply.
I'll add it to that page in the next few days. It has a 50 ohm input
impedance and can be driven from a splitter which is in turn driven by
another such amplifier to form a high reverse isolation and channel to
channel isolation, low noise distribution amplifier.
Whatever you do don't copy JPL's isolation amplifier designs they are
relatively noisy particularly in the flicker noise region.
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