[sdiy] Op Amp LED driver / Current Source problem/solution

[Tim Ressel]

I hadn't thought of that. Most of the LEDs I use are so bright that I have to turn the current done to 5mA or less. 

Tim Ressel
Circuit Abbey
503-750-9331
timr at circuitabbey.com




________________________________
From: Neil Johnson <neil.johnson71 at gmail.com>
To: Tim Ressel <timr at circuitabbey.com> 
Cc: Justin Owen <juzowen at gmail.com>; SDIY List <synth-diy at dropmix.xs4all.nl> 
Sent: Friday, November 28, 2014 9:16 AM
Subject: Re: [sdiy] Op Amp LED driver / Current Source problem/solution


Tim Ressel wrote:
> I am wondering if an inverting circuit work better:
> http://www.sdiy.org/brotheo/LedDriver.png
>
> You probably still need a resistor to null the DAC offset at zero output.

Umm, the problem with that circuit is that the input also supplies the
LED current, so you are loading the signal you are monitoring.  Not so
good for LEDs that take lots of mA.




Neil
--
http://www.njohnson.co.uk