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

[usenet at teply.info]

On 10.04.22 11:50, Leon Pavlovic wrote:
> What would be a (very) good lab setup for the 1/f noise evaluation? I'm
> talking about BJTs and JFETs.
> 
> What instrumentation and power supply are needed? How not to measure in a
> wrong way - like 1/f noise in the instrumentation or the power supply
> circuitry? Active collector/drain current sources vs pure resistive...
> 
> I'm quite familiar with the low NF measurements, so I guess the same
> practice would apply: insert your DUT, short its input side, have a
> low-noise post amp and display the noise on FFT SA?
> 
In principle, the setup for 1/f is not so different from low Noise 
Figure measurements. A sufficiently low noise post amp, sampling and FFT 
is pretty much what's used even in commercial test systems. If you are 
after corner frequencies of a few kilohertz at most, even sound cards 
can be used for sampling. Sure, most sound cards need modification in 
order to make them useable at frequencies below 20 Hz.

What's a bit more involved is the biasing of the DUT, which needs to be 
sufficiently low noise to not degrade your measurement, and the low 
noise preamp, which also needs be be better than your DUT. Sometimes 
you'll need to resort to battery supplies in order to get rid of mains 
noise coming in.

I'm sure others can and will chime in here with recommendations.

Florian