ALD mosfets

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mikep

Well-known member
Joined
Feb 18, 2006
Messages
450
Location
Philadelphia
from Advanced Linear Devices
I just noticed these matched mosfet pairs like ald110802. I dont notice any noise spec on the datasheet but the Vgs matching looks pretty good. the high input impedance could make these useful for certain things. like DIs, discrete servos. I can deal with the low voltage, but that puts an even higher expectation for the noise. Has anyone tried these devices?

mike p
 
In general when they don't spec noise or noise figure data one should be suspicious of noise performance. Even if samples appear OK, without a spec they might change in production.

JR
 
IIRC these folks have managed to fine-tune gate thresholds as to allow circuits functioning at ever-lower voltages, and hence potentially lower powers.

Although MOSFETs have made amazing strides in reducing low frequency noise, the surface state/interface state trapping phenomena make them likely to always be inferior to junction FETs for voltage noise.
 
good point, that no spec could mean lots of variation in production. but they specifically boast consistency in their documents.

I dont dislike JFETS, this would be something in addition to, not instead of. by the way, where is the p-channel dual JFET to go with the LSK389? yeah I dont know, I was thinking aloud. ill probably never get around to trying them. I use alot of NMOS for discrete logic, level shifing, load switching.

the voltage range is +/-6v. guitar pedals, other 9v battery applications come to mind. ever hear a Z-Vex SHO (super hard on) pedal? Im reasonably certain thats a single enhancent mode mosfet in common source. sounds fantastic on guitar, bright but good. cant you use a mosfet like a jfet, as a variable resistor in shunt? the high input resistance+low leakage could help in looooong time constant analog control loop integrators, no?

mike p
 
> the voltage range is +/-6v. guitar pedals, other 9v battery applications come to mind

Those zero-bias FETs can run on +/-0.1V supplies. Which is stupid for most audio. But a single AA-cell could power a pedal pretty much until all the rust runs out the end of the battery; no mode dead-battery blues, or not for several years. The peak 0.5V output will put any geetar amp input to full wail. The lkely high noise level may be acceptable, since guitar pickups evolved to overcome the fairly high self-noise of a selected 5%-rejected 12AX7/7025.

One of their design papers does show variable resistance and the apparently linear range appears to be 0.3V both ways over a wide range of R. I dunno if that is Truth or hasty drafting.
 
[quote author="mikep"] ever hear a Z-Vex SHO (super hard on) pedal? Im reasonably certain thats a single enhancent mode mosfet in common source.
[/quote]

Maybe:
http://analogguru.an.ohost.de/193/schematics/Zvex_SHO.gif

cheerz
ypow
 

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