[sdiy] Bicolor LED driver?

[Grant Richter]

You can get two pin bi-color LEDs. Just connect them via a 1K  
resistor to op-amp output and other pin to ground.
Mouser part number 604-L937EGW

This LED is on bi-polar outputs in Wiard modules.
Wiard uses Green = GO = positive, Red = STOP = negative
Blacet uses the opposite, naturally.

On Nov 24, 2005, at 2:39 PM, Luís Marka wrote:

> Hi gang,
> I decided to use bicolor LEDs to indicate output voltage in a few  
> modules (LFOs, for example). The idea is to have the red LED going  
> ON for positive signals, and the green one for negative. So far I  
> am driving the red half of the LED with a standard NPN transistor  
> buffer, and the green half via an inverter operational amplifier at  
> unitary gain followed by an identical buffer. The LED is a 3-pin,  
> with a common catode.
> Question: Is there a simpler way to do that? It would be great if I  
> could get rid of the op. amp, this would save quite some space on  
> the boards and simplify the layout, especially when I drive several  
> LEDs in one module!
>
> Best,
> Luis Marka
>