Noise Measurement Amplifier

[lcsaszar]

I created for myself a x100 gain low-noise measuring amplifier with NE5534AN. It is powered from 2x 9V batteries and has a DC blocking input capacitor.

 

[EdGr]

A microphone pre-amplifier with a DC blocking capacitor should work. You may have one already.
Ed

 

[rsavas]

2SK3557-6-TB-E is a possible replacement. One could try 2SK209 as well. Since I had a enough BF862 to build mine, I did not try 2SK3557-6-TB-E, even though I bought enough of them to use but did not perform a second build.
This is the Mouser shopping cart I put together for my build
https://www.mouser.ca/ProjectManage...jectGUID=3a263434-d02b-4f65-859b-ffa8831c6f0a

 

[gerhard]

cph3910

< https://www.digikey.de/de/products/...-E/4847608?s=N4IgTCBcDaIMYAcAWBmAnARgAwgLoF8g >

Fits on sot-23, 16 pcs. in par. got me 0.35 nV/rt Hz at Id = 47 mA total.
NSVJ3910 is the same, IIRC even same marking. You cannot tell them apart
when taken out of the tape.

There are also JFE140 by TI, not pin compatible, but with protection diodes.
There is a thread on them started by TI FAEs in the sellers section.
Performance-wise in the same class. I have a few, but not tested.

< https://www.diyaudio.com/community/threads/ultra-low-noise-jfets-from-texas-instruments.375079/ >

 

[Mark Tillotson]

The CPH3910 is an RF JFET, it will likely have a high 1/f knee as this usually isn't important for RF devices (except those meant as oscillators).
BTW the TI part is the JFE150, not JFE140.

 

[rsavas]

BF862 is a RF jfet as well but that’s what Sam chose to use so I followed along.
So is 2SK3557-6-TB-E, intended for RF, to bad no 1/f graphs in the specs.
Maybe 2SK209 is a better choice since it’s not an RF jfet.

 

[tombo56]

2SK3557-6-TB-E is a very good choice. It has some 10% higher noise than BF862 but very low 1/f noise corner. Precisely calibrated measurement of my build.

 

[gaszto]

Thank you, I already ordered a pcb from JLCPCB and I will go with 2SK3557-6-TB-E

 

[bucks bunny]

wow, that is impressive

 

[rsavas]

Something strange just happened to the Mouser shopping cart I referenced above, there is only one item in the cart now, so how did that happen?
I'll call Mouser support

 

[gaszto]

The link is pointing me onto the Mouser web page

 

[rsavas]

What web page? "Cart:SG LN preamp"
Were you in there deleting all the parts? I have an investigation going on as to what happened to all the items in the cart.

 

[gaszto]

https://eu.mouser.com/

 

[rsavas]

If you use this link what do you see?
https://www.mouser.ca/ProjectManage...jectGUID=3a263434-d02b-4f65-859b-ffa8831c6f0a
does it take you to
https://eu.mouser.com/

 

[gaszto]

If I clicking onto the link, it's opening https://eu.mouser.com/ instead of any shopping cart

 

[rsavas]

okay I'll ask them why that is thanks

 

[gerhard]

2 hours ago, everything was still there. I was asked if
I'm in .ca or .de
I clicked on Germany.

 

[rsavas]

Weird, all items still there now? Mouser gremlins or folks messing with me?

 

[gerhard]

no, only 1 part that is out of stock / eol.
my own basket is still full, mostly EMI shields.

 

[rsavas]

Thanks, now need to figure out why everything was deleted except the "only 1 part that is out of stock / eol"
"Crap" is all I can say for now, so much for trying to help folks out on a public forum, won't be doing that again until I figure out what's going on.