[time-nuts] how to find low noise transistors (was: Firmware and antenna for Stanford Research FS700)

Bob Camp kb8tq at n1k.org
Sat Jul 18 08:29:33 EDT 2015


You have (and always have had) two basic choices:

1) Buy a very expensive part from somebody who has gone to the trouble 
of characterizing the noise performance and will guarantee at least some
of what they show on the data sheet. 

2) Buy a bunch of cheap transistors and test them. Lock in on a
specific part and vendor. Keep monitoring what you get in case they “improve”
their process and the magic goes away. 

How do you select candidates? That’s never been easy, there is less and
less data on the sheets every day. Normally the first step is to look at
a vendor that you have had luck with in the past. The next step is to ask them…


> On Jul 18, 2015, at 5:16 AM, Attila Kinali <attila at kinali.ch> wrote:
> On Fri, 17 Jul 2015 23:25:10 -0400
> Charles Steinmetz <csteinmetz at yandex.com> wrote:
>> A pair of Zetex (Diodes, Inc.) 
>> ZTX849 or FZT849 actually have significantly lower voltage noise than 
>> either the LM394 or MAT12.
> I always wonder how you figure out whether a transistor is low noise
> or not. What part of the datasheet hints at which transistors have low
> noise and which have not? Even if it's just try and measure, how
> do you find good candidates to measure?
> 			Attila Kinali
> -- 
> I must not become metastable. 
> Metastability is the mind-killer.
> Metastability is the little-death that brings total obliteration.
> I will face my metastability. 
> I will permit it to pass over me and through me. 
> And when it has gone past I will turn the inner eye to see its path. 
> Where the metastability has gone there will be nothing. Only I will remain.
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