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

[Bruce Griffiths]

The phase noise specifications for an amplifier are meaningless if the input signal level isnt specified.
Bruce
> On 11 January 2020 at 03:27 Leon Pavlovic <leon.pavlovic at gmail.com> wrote:
> 
> 
> The HP K22 had a specified noise figure as <7.5dB (I'm guessing its NF is
> not around 1dB) and the measured noise floor -175dBc/Hz at 10kHz and up at
> 400MHz from the datasheet.
> 
> Since I've had a need for a low-gain (2-4dB) isolation amp at the
> 100-500MHz range, I've experimented with a cascode design with Infineon's
> BFR106. Measured PN: -151dBc at 100Hz, -161dBc at 1k, -171dBc at 10k and -178dBc at
> 100k and up (@400MHz). P1db should be around +15dBm and the NF was not
> measured yet.
> 
> Cheers,
> Leon
> 
> 
> >
> > ---------- Forwarded message ----------
> > From: John Miles <john at miles.io>
> > To: "'Discussion of precise time and frequency measurement'" <
> > time-nuts at lists.febo.com>
> > Cc:
> > Bcc:
> > Date: Thu, 9 Jan 2020 22:23:23 -0800
> > Subject: Re: [time-nuts] low phase noise, noise floor and noise figure
> > amplifier at 400MHz
> > > 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
> >
> >
> >
> >
> >
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