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Old 10th February 2006, 02:27 PM   #1
Young is offline Young  United States
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Default Which is the lowest noise FET?

Hi everyone!

Does anybody have a thorough comparison of the noise level between various FETs?

I am looking for a FET with the lowest noise, low current (<1mA), low voltage (<=3.3V), and surface mount package. I want to use it as the first stage of my amplifier.

The old 2SK170 and 2SK369 seem to be out. I searched at Toshiba home site, but there is no list there.

There are a number of Op Amps out there, but they are not what I am looking for.

Thanks for any responses.

Best regards, Young
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Old 10th February 2006, 02:33 PM   #2
mlloyd1 is offline mlloyd1  United States
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look for a company called InterFET at www.interfet.com

unless you manage to get a sample or two, be prepared to spend $$

mlloyd1
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Old 10th February 2006, 03:04 PM   #3
lineup is offline lineup  Sweden
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Quote:
Originally posted by mlloyd1
look for a company called InterFET at www.interfet.com

unless you manage to get a sample or two, be prepared to spend $$

mlloyd1
You can download InterFET 'Whole databook' ( I did! )
it is a 189 pages PDF with data of their JFET:
http://www.interfet.com/jfet.htm

Also you can request this paper from InterFET:

Methods of Reducing Noise of Junction Field
Effect Transistor (JFET) Amplifiers

H. E. Kern, J. M. McKenzie (Bell Telephone
Laboratories, Inc.)
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Old 10th February 2006, 04:39 PM   #4
Bensen is offline Bensen  Belgium
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Hi,

Three months ago I ordered 6 x 2SK389BL and 6x 2SJ109BL FET's at:

http://www.donberg.ie/


Greetz
Ben
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Old 10th February 2006, 05:15 PM   #5
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As the Toshibas are out, Interfet would be one choice, but at least in Europe not easy to come by...

So what remains?

Something like BF 998, BFR 30/BFR 31, but i have no idea how they sound?
At least they are low noise...

Regards
Michael
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Old 10th February 2006, 05:25 PM   #6
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you might be able to get some samples from Linear Systems -- they advertise in AudioXpress (which is a good sign) but they don't have a typical distributor like Mouser or DK: www.linearsystems.com --

I have some TO-92 (non-surface mount): http://www.tech-diy.com/smallsignal.htm if you get stuck.
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Old 10th February 2006, 06:04 PM   #7
lineup is offline lineup  Sweden
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you should be able to find 2SK170 and 2SK389 in Europe
no problem
do some search for electronic components providers

for example at www.dalbani.co.uk
http://www.dalbani.co.uk/electronic_...stors.php?p=41|
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Old 10th February 2006, 06:48 PM   #8
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interFET does have LSK389 (= 2SK389).
But they do not have 2SJ109.
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Old 10th February 2006, 11:27 PM   #9
Young is offline Young  United States
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Default Thanks, but my question is which is the best!

I suspect there must be a reason that Toshiba took those FETs out, and they should have been replaced by some better ones.

170 and 369 are not SMD. Let me tell you a secret: according to my experiments, SMD has much better performance than TO-92! My interpretation is the leads are much shorter!

Thanks again, Young
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Old 11th February 2006, 01:57 AM   #10
jcx is offline jcx  United States
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if en in jfets is ~ porportional to 1/sqrt(gate area) then these should win:

http://www.lovoltech.com/pdf/LD1014D.pdf

of course the 1/f corner may be anywhere as they really won't be tracking on obscure process dependencies for pwm switches

anyone try for a noise measurement of these (pass forum?)

"best" is as usual contex/application/system dependent, Power Amp w/line input?, mc pre? what do you really need?
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