Jelly bean N FETS

[Martin Griffith]

I've got to enbrighten some lumileds, for a brief period, say
50-100msec, using an external current limit resistor, say
350mA,running off 4 AA cells.
There are so many fets out there, which jelly bean?
SOT23 or PTH

Must be Joerge approved


martin

 

[Joerg]

I've got to enbrighten some lumileds, for a brief period, say
50-100msec, using an external current limit resistor, say
350mA,running off 4 AA cells.
There are so many fets out there, which jelly bean?
SOT23 or PTH

Must be Joerge approved

2N7002:
http://www.onsemi.com/pub_link/Collateral/2N7002E-D.PDF

Pulsed isn't spec'd above 10usec and the 5sec rating is under 350mA so
if that feels iffy you might want to parallel two of them. Under $0.03 a
pop in qties

The Vgs spec for 4.5V Vgs is also a bit hokey. Up top it says 3ohms max
at 310mA, farther down they repeat that and state only 50mA. But they
handle high currents quite well. Depends on how often your 100msec
pulses happen.

--
Cordialmente, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Martin Griffith]

2N7002?

John

I'd thought of that, but the max Rdson seems a bit high, 5to13R
depending on the wind direction when the fet was made ( fairchild
datasheet)
I'd like to make the external R determine the current, rather than
the fet.
There is enough room for a T0220, but that just seems silly to light
up a silly, but quite important, little LED


martin

 

[Spehro Pefhany]

I've got to enbrighten some lumileds, for a brief period, say
50-100msec, using an external current limit resistor, say
350mA,running off 4 AA cells.
There are so many fets out there, which jelly bean?
SOT23 or PTH

Must be Joerge approved


martin

Why use an expensive MOSFET if a cheap BJT will do?

Eg. 8050 typical 0.28 Vce(sat) at 800mA (equivalent to 0.35 ohms) @
Ic/Ib = 10.
Best regards,
Spehro Pefhany

 

[Joerg]

I'd thought of that, but the max Rdson seems a bit high, 5to13R
depending on the wind direction when the fet was made ( fairchild
datasheet)
I'd like to make the external R determine the current, rather than
the fet.
There is enough room for a T0220, but that just seems silly to light
up a silly, but quite important, little LED

How about this one then:
http://www.onsemi.com/pub_link/Collateral/NTA4153N-D.PDF

SC75 meaning really tiny, but a tad over 10 cents.

 

[Martin Griffith]

Why use an expensive MOSFET if a cheap BJT will do?

Eg. 8050 typical 0.28 Vce(sat) at 800mA (equivalent to 0.35 ohms) @
Ic/Ib = 10.
Best regards,
Spehro Pefhany

wow, never heard of a 8050 before, got a URL? a quick google for
2n8050 just provided damn chinamart crap


martin

 

[Joerg]

I'd thought of that, but the max Rdson seems a bit high, 5to13R
depending on the wind direction when the fet was made ( fairchild
datasheet)
I'd like to make the external R determine the current, rather than
the fet.
There is enough room for a T0220, but that just seems silly to light
up a silly, but quite important, little LED

If you want to switch to an almost dead short check this one out but
it'll cost around 15c:
http://www.zetex.com/3.0/pdf/ZXMN3A01F.pdf

Also quite good at 11c:
http://www.fairchildsemi.com/ds/ND/NDS351AN.pdf

Now this one really ought to do it, at 12c:
http://www.onsemi.com/pub_link/Collateral/NTR4501N-D.PDF

 

[Martin Griffith]

2N7002:
http://www.onsemi.com/pub_link/Collateral/2N7002E-D.PDF

Pulsed isn't spec'd above 10usec and the 5sec rating is under 350mA so
if that feels iffy you might want to parallel two of them. Under $0.03 a
pop in qties

The Vgs spec for 4.5V Vgs is also a bit hokey. Up top it says 3ohms max
at 310mA, farther down they repeat that and state only 50mA. But they
handle high currents quite well. Depends on how often your 100msec
pulses happen.

Thanks, just had a bad day with the UK/EU Farnell/RSwww search
enginzz, they have all this teknologeewhizzcrap and they dont have a
column of <RdsOn, or Vgs >5 etc.

Bad day, time for zzz, or a video maybe "Bad Day at Black Rock"
is applicable, or maybe the winavr help files (nooooooway)

Ugh


martin

 

[Martin Griffith]

If you want to switch to an almost dead short check this one out but
it'll cost around 15c:
http://www.zetex.com/3.0/pdf/ZXMN3A01F.pdf

Also quite good at 11c:
http://www.fairchildsemi.com/ds/ND/NDS351AN.pdf

Now this one really ought to do it, at 12c:
http://www.onsemi.com/pub_link/Collateral/NTR4501N-D.PDF

Joerge for President........................(of S.E.D)


martin

 

[Joerg]

Thanks, just had a bad day with the UK/EU Farnell/RSwww search
enginzz, they have all this teknologeewhizzcrap and they dont have a
column of <RdsOn, or Vgs >5 etc.

Don't expect "web designers" to learn, start your own parts wiki ;-)

Check out the other FETs from my last post, some pretty hot ones there
if the BOM budget can stomach 10-15c for the FET. Else it'll have to be
the old 2N7002.

Bad day, time for zzz, or a video maybe "Bad Day at Black Rock"
is applicable, or maybe the winavr help files (nooooooway)

C'mon, it ain't even midnight over there yet. Time for an eye on town,
maybe a cerveza (mas grande) or a Rioja.

 

[Joerg]

Joerge for President........................(of S.E.D)

Thanks, but no thanks. I've seen how presidential candidates were torn
to shreds in this here newsgroup ;-)

 

[Martin Griffith]

Don't expect "web designers" to learn, start your own parts wiki ;-)

Check out the other FETs from my last post, some pretty hot ones there
if the BOM budget can stomach 10-15c for the FET. Else it'll have to be
the old 2N7002.



C'mon, it ain't even midnight over there yet. Time for an eye on town,
maybe a cerveza (mas grande) or a Rioja.

I live in a sleepy town,even the kidz on mopeds have gone too sleep by
now, 23:31hrs, made a miserable tortilla, but the rioja is working


martin

 

[Joerg]

Now I wonder why they don't have SOA curves for a 20-V, 3.2-A MOSFET in
a SOT-23 package....probably because the curves wouldn't be
distinguishable from the Y axis...

Yeah, they are meant for switching. Operate a bunch of them in linear
fashion for more than a few milliseconds and it's like the O.K. Corral
after Doc Holliday drew his pistol

 

[[email protected]]

wow, never heard of a 8050 before, got a URL? a quick google for
2n8050 just provided damn chinamart crap

martin

first hit for 8050 npn is SS 8050 fairchildsemi

-Lasse

 

[Joerg]

first hit for 8050 npn is SS 8050 fairchildsemi

Problem with those is they are not SOT23 and hfe can be less than 50 at
a few hundred mA Ic. That can become a bit tight if Martin wants to
drive it with a wimpy uC or something.

 

[mpm]

I've got to enbrighten some lumileds, for a brief period, say
50-100msec, using an external current limit resistor, say
350mA,running off 4 AA cells.
There are so many fets out there, which jelly bean?
SOT23 or PTH

Must be Joerge approved

martin

Not to be a language cop or anything, but I don't believe "embrighten"
is a real word.
I looked it up in several online dictionaries because I thought maybe
I didn't know this one...

"embright" is a word (a transitive verb), and it does mean to
illuminate, but is considered obsolete. I could not find
"embrighten", or any other obvious variant, anywhere. FYI.

-mpm

 

[Joerg]

Not to be a language cop or anything, but I don't believe "embrighten"
is a real word.
I looked it up in several online dictionaries because I thought maybe
I didn't know this one...

"embright" is a word (a transitive verb), and it does mean to
illuminate, but is considered obsolete. I could not find
"embrighten", or any other obvious variant, anywhere. FYI.

http://en.wiktionary.org/wiki/Citations:embrighten

But it does sound rightpondian, I've never heard it in the US. And
Martin mentioned he'd already had some rioja

 

[Hammy]

I've got to enbrighten some lumileds, for a brief period, say
50-100msec, using an external current limit resistor, say
350mA,running off 4 AA cells.
There are so many fets out there, which jelly bean?
SOT23 or PTH

Must be Joerge approved


martin

Have you seen the the BSS138.

http://www.fairchildsemi.com/ds/BS/BSS138.pdf


Newark has the BSS138LT1G for 0.04 cents small quantity SOT-23.

Another possiblity may be the NTS4001.

10 cents from Newark sc-70

http://www.onsemi.com/pub_link/Collateral/NTS4001N-D.PDF

I have about fifty of each,easy drive requirments.

 

[Hammy]

Have you seen the the BSS138.

http://www.fairchildsemi.com/ds/BS/BSS138.pdf


Newark has the BSS138LT1G for 0.04 cents small quantity SOT-23.

Another possiblity may be the NTS4001.

10 cents from Newark sc-70

http://www.onsemi.com/pub_link/Collateral/NTS4001N-D.PDF

I have about fifty of each,easy drive requirments.

The NTS4001 doesnt have an SOA chart but if you want I can perform a
simple test 350mA at 100mS VGS 3.5.

 

[Spehro Pefhany]

Problem with those is they are not SOT23 and hfe can be less than 50 at
a few hundred mA Ic. That can become a bit tight if Martin wants to
drive it with a wimpy uC or something.

Fairchild is one source, but they are generic and very common in
designs for offshore manufacturing if you don't need a very high Vceo.
TO-92 like the 2N7000. The "D" beta bin is only marginally more
expensive.


Best regards,
Spehro Pefhany