[sdiy] Bi-colour LED

[Theo]

Yes, but the current part is not my idea.
It's a well known CV indicating circuit.
Just that with two extra diodes you can use it with three legged LED.

Theo

----- Original Message -----
From: Jaroslaw Ziembicki <aon.912230836 at aon.at>
To: SDIY <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, July 04, 2004 7:11 PM
Subject: Re: [sdiy] Bi-colour LED


> ----- Original Message -----
> From: "Theo" <t.hogers at home.nl>
> To: "Jaroslaw Ziembicki" <aon.912230836 at aon.at>; "Rob Keeble"
> <rob at emulatorarchive.com>
> Cc: "SDIY" <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, July 03, 2004 5:40 PM
> Subject: Re: [sdiy] Bi-colour LED
>
>
> > Just one opamp, one resistor, the duo LED and two diodes (1N4048) will
do.
> > Opamp + input to ground
> > Resistor is the input and goes to the opamp - input.
> > Now the feedback loop:
> > The anodes of the dual LED go to the output and - input of the opamp.
> > To the common cathode of the LEDs you connect the anodes of the diodes.
> > Cathodes of the diodes again connect to output and - input of the opamp.
>
> Note: the circuit described here has a great property:
> the CURRENT of the LEDs (instead of voltage) is proportional to the input
> voltage. That means, the LEDs' nonlinearities don't matter.
> Once more - my compliment, Theo...
>
> Kind regards
> Jarek
>
>
>