[time-nuts] low phase noise, noise floor and noise figure amplifier at 400MHz

[John Miles]

> Any suggestions on topologies, transistors, white papers, etc?  I'm
> considering the NXP BFU590Q silicon bipolar transistor, which I have used
in
> a transformer feedback configuration at 100MHz with less than -180dBc/Hz
> PN.

You could take a look at the approach behind the option-K22 amplifiers that
were sold by HP for use with the 3048A.  I've got one of those but I needed
a couple more of them at one point, so I built some (literally) quick and
dirty copies with BFG591 transistors with good results.  

I've mentioned them before on here, I think.  There are a few photos and
plots at http://www.ke5fx.com/k22.htm .  Basically a CE amplifier with an
LED-referenced bias stage originally suggested by Bruce Griffiths.

A single stage won't deliver the gain you're after, but these amplifiers are
relatively well-behaved and can be cascaded at will.  That was the original
intent with the K22, which consisted of two independent amps in one box.  If
you want to use the K22 amps to keep oscillators from injection locking, you
pretty much have to cascade them due to lack of reverse isolation.  The
homebrew hack job is similar to the HP original in most respects including
that one.

I'd be inclined to use a dual-emitter part (BUF590G) instead of the BUF590Q,
if I were building more of these.

-- john, KE5FX