As shown here, with the load on an npn collector that's called "common emitter" and if it's below the emitter that's "emitter follower".
It's not intuitively clear to me where the terms come from... can someone elucidate please? What do they mean?
"Common emitter" means that the emitter is "common" to the input (Base/emitter) and output (Collector/emitter) - the emitter is directly connected to the common ground.
On an npn, it's about limiting the current from the arduino pin...
Via a resistor to base, and you'd be fine ... but under emitter follower, swap the base transistor out and move it betwewn ground and the emitter..
Now even though there's no base transistor it's safe in the emitter follower example
JimboZA:
It's not intuitively clear to me where the terms come from... can someone elucidate please? What do they mean?
the common collector configuration is also called "emitter follower" , just because the output 'follows' the input (unity voltage gain)