On Thu, 18 Jun 1998, Thomas McGahee wrote:

> A better solution is to use an NPN transistor with a base resistor of about
> 330 ohms. Connect the emitter to ground (Vss), connect the cathode
> of the IR LED to the collector. Connect a current limiting resistor
> from the anode of the IR LED to +5. A high out from the PIC will
> cause the IR LED to emit infra-red light.

I see. But I think one could spare the base resistor by using an emitter
follower, right? I mean connecting base to PIC output, collector to +5V
and placing diode/resistor between emitter and GND. This cuts the drive
voltage for the diode/resistor combination by 0.7V, but has better
switching characteristics as the transistor is not put into saturation.
Right?

Georg.

BTW, thanks to all that contributed to this.