Anyone have a cheaper source for the NTE2987 NMOS. Mouser wants like $7 for one.
Either that or an equivalent part???

 

12A 60v 33 cents
http://octopart.com/info/ON Semiconductor/MTP3055VL


27A 60v 36 cents
http://octopart.com/search?q=HUF76419D3

OCTOPART

http://octopart.com/search?q=logic+level+N-Channel+Mosfet&c=0&d=0

And it's good when you've gotten the part number as it goes and gets prices. I use Digikey myself. It's the cleanest parts and datasheet search on the web.

http://octopart.com

The URL at the bottom of your message is a dead link.

 

Link changed to picture in my first post.


It's a Linear Constant Current LED Dimmer...
The NMOS in the circuit seems overkill though, but maybe i'm not getting the full picture...

 

I don't know if it is a good idea to parallel the three LEDs as you have shown. The voltage drop across the LED is bound to vary between each of the LEDs. The LED with the lowest forward voltage will receive a greater share of the current than the remaining two and thus be brighter. This difference may be small enough that you can ignore it. You just need to be aware that it exists.

hgmjr

 

The voltage drop across the LED is bound to vary between each of the LEDs.hgmjr

Unerstood... There will probably be more that 3-4 LED's in parallel also.

How would you go about selecting LED's for equal or close voltage, use a constant current source and measure the voltage drop across them, matching the ones that are the closest?

Also: the only specific requirements of the MOSFET is that it is fully on at 400mA whth Vgs < 3.2V and it must be Logic-level.

 

Can you provide us with a part number so that we may take a look at the Vf and the current rating of the white LEDs you plan to use?

hgmjr

 

Can you provide us with a part number so that we may take a look at the Vf and the current rating of the white LEDs you plan to use?

hgmjr

The LEDs are rated 10,000 to 12,000 mcd output. Operates from 3.2 to 3.4VDC @ 20mA.

I don't have a part#

Will probably design for 17-18mA and 3.2V...