[time-nuts] Re: +1/f of transistors

[ghf at hoffmann-hochfrequenz.de]

Am 2022-04-15 21:13, schrieb Richard (Rick) Karlquist:
> When I was working on a cold atom Rb standard a few years ago,
> I settled on the LT1028 with a 3.5 Hz (yes Hertz) noise corner and
> noise floors of less than 1nV/sqrtHz and 1pA/sqrtHz.  GBP>50 MHz.
> Specified on the data sheet.  In production now for ~40 years!  I can
> remember when it first came out.
> 
> What's not to like about this?  Are low flicker discreet transistors
> still  needed?

Ooohps, that one was sent while uploading the 2nd picture. Weird.
The first post is very redundant. Very redundant, that's what it is.

I would not call that a 3.5 Hz corner frequency, esp. for the
current. And also, I do not like the noise hump at > 200 KHz that was
undisclosed for > 35 of the 40 years. I also do not like the new
prices, but that also goes for the AD797.

ADA 4898-2 seems to deliver most for the $.
Two amplifiers for half the price.

TI guarantees not much for their LT1028 clone, but then I also
got LT1028 from a local Maxim distributor, many years ago.
Must be quite exotic.

Gerhard
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