[sdiy] LEDs as diodes

[Oren Leavitt]

I occasionally see LEDs used in power amplifiers to set the bias thresholds in class AB output stages.

-----Original Message-----
From: Magnus Danielson <cfmd at bredband.net>
Sent: Dec 21, 2004 10:51 AM
To: rtellason at blazenet.net
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] LEDs as diodes

From: "Roy J. Tellason" <rtellason at blazenet.net>
Subject: [sdiy] LEDs as diodes
Date: Tue, 21 Dec 2004 13:01:04 -0500
Message-ID: <200412211301.04328.rtellason at blazenet.net>

Roy,

> One application that I never could figure was done in certain Yamaha power 
> amps...
> 
> They used LEDs of a type I'd never seen before -- these looked like regular 
> glass-bodied rectifiers.  But they were in fact LEDs,  and if you looked real 
> close you could see some light coming out of there.  I don't know if it's a 
> different temperature characteristic,  or some other aspect of things,  but 
> at one point I had to get myself a few of these.  :-)
> 
> I haven't done anything with them yet,  though.

You can use them as voltage references sort of. I've seen certain amplifeir
designs using it. XELEC I beleive one was called (it was many years ago I saw
one).

Instead of stacking a bunch of diodes or Zeners you use LEDs. I don't recall
the characteristics thought. The low light level is probably because they don't
have much standing current in that design, it is not he light emitting side of
things which is important.

Cheers,
Magnus