I want to protect the output pins of a microcontroller so that when I connect to other devices (that may accidently short to ground). Up until now I have been using a discrete npn transistor in common collector configuration to act as a voltage follower and to simultaneously drive an output led.
This works fine and is small (tiny transistor and a few resistors) but when I am using a lot of outputs that I would like to protect it would be nice to lower the part count.
Is it better to use a quad opamp configured as for voltage followers? or a hex/octal buffer IC? If the latter, what is a good IC to use?
The leds I drive are low current (<2mA) and I am typically driving 100k loads (or high impedence)
If you only have to worry about shorts to ground then a device like the 74LS05 or similar might do the trick. It's a hex inverting open collector driver and is hardier than the CMOS version.
The 74LS07 is open collector buffer with higher voltage output ability.