[time-nuts] Effect of EFC noise on phase noise

[Gerhard Hoffmann]

Am 02.08.2016 um 02:42 schrieb Bruce Griffiths:
> /"I'm working on a new amplifier based on IF3602 or BF862 FETs that can
> use 10u foil only."/
> /
> /
> Similar to that published by Groner in Linear Audio?
> /
> /
I know that Groner exists from some web site, but had no personal contact.
Also I don't read Linear Audio other than 2 articles from Scott Wurcer 
that I've bought.
I highly regard Scott, he's the father of the AD797 after all and AD fellow.
I also had some conversations with him on that.

The preamp will be classical.  Some JFETs in parallel, no source 
resistors except
half an Ohm for feedback, more would add to the input noise voltage.
Cascode with a Zetex bipolar (or whatever they are called now).
OP37 for loop gain. feedback from OP37 output for 50 or 60 dB gain.
Post amplifier to 80 db or so.
Without the cascode, the 1 MHz is not possible. It does not help that
the feedback limits the voltage excursions on the drain.

I'm not yet sure about the effective input capacitance. I get abt. 1 or 
1.5 MHz
bandwidth from a low impedance source. A few nF on the input capacitance
would be ok, in the end I want it after a ring mixer for phase noise 
measurements
but I get unreasonably more in simulation, depending on if I measure it from
upper frequency corner with a larger input resistor or the resonance 
frequency
with an added inductor.

You can get the LTspice file if you like.

regards, Gerhard