Does anyone know some good small-signal MOSFETs?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

user 37518

Well-known member
Joined
Nov 15, 2008
Messages
2,233
Location
-
I've looked around for small signal MOSFETs but all I can find is the typical power MOSFET, I would like something in to-92 package or even smd.  A quick search in Mouser revealed the BS170 but seems to be optimized for power rather than audio, Any suggestions?
 
AFAIK MOSFETS are generally not considered for very low noise applications. 

I looked at a few data sheets I had around from my outlet tester design (I used SMD MOSFETs for their high input impedance). The two datat sheets I just looked at do not even specify noise or NF.

Using google I found a "low noise" MOSFET specifying a respectable 1 dB Noise Figure but at 400 MHz  :eek:, somewhat above the audio band.

JR

PS: FWIW the semi industry played around with mosfet op amps back in the 80's but AFAIK these never gained popularity. More recently I've seen some CMOS (low current, low voltage, rail to rail) op amps that presumably are reasonable.  https://www.analog.com/media/en/technical-documentation/data-sheets/6244fb.pdf  This part spec's 8nV/rt Hz which doesn't suck, but is not as good as modern bipolar uber opamps
 
I understand (The Art of Electronics, 3rd. Edition) that jfets are less noisy, but for both jfets and (small-signal) MOSfets, there are fewer and fewer parts available. A series of jfet part numbers listed in that book (again, 3rd Edition, 2015, three years ago) are now no longer made.

There's also the Toshiba 2sk170 that appeared to be popular in audio applications but also no longer made, though there's this other company apparently making and selling them at "somewhat" higher prices:
https://www.diyaudio.com/forums/pass-labs/317563-replacement-toshiba-2sk170-2sj74.html
 
Thanks for all the info, I will check them out, have you guys tried using this parts?


@benb : diyaudio is selling a pair of matched JFETs for 48 dollars! jeez
 
user 37518 said:
Thanks for all the info, I will check them out, have you guys tried using this parts?


@benb : diyaudio is selling a pair of matched JFETs for 48 dollars! jeez
JFETs are different animals from mosfets with many low noise versions.

JR
 

Latest posts

Back
Top