AVR-Chat

Tom Becker wrote:
>  > ... switching both leds On.
> 
> Or off; your choice.  If you put the loads on the collectors, the base 
> current path you describe will turn both on if the control pin floats.
> 
> If you put the loads on the emitters, the switches become emitter 
> followers.  That makes a control dead zone where neither LED will be on 
> if the control pin floats since both bases are cut off.

You could rely on the 2 x(LED + 0.7) voltage drop to be less than 5VCC, so
2*(2.1+0.7) = 5.6V which is a bit marginal for my liking. You could add extra
diodes for more voltage drop. It's not really my style of design tho.

                   +5VCC
               --+------+--
                _|_     |
            LED \ /     |
                ---     |
                 |      |
                 >      |
                 <      |
                 >      |
                e|      |
AVR       PNP |/       |
---+      +---|        |
    |pin   |  b|\       |
    +------+    c|     c|
    |      |     |   b|/
---+      +----------|  NPN
                 |    |\
                 |     e|
                 |      >
                 |      <
                 |      >
                 |      |
                 |     _|_
                 |     \ / LED
                 |     ---
                 | GND  |
               --+------+--