5v to 3v logic...

I was curious about a transistors behavior when a higher voltage is placed on it’s base over the collector.

I’m unsure about this circuit, is this a safe way of shifting down (5v to 3) voltage?

Its called saturation, the collector current stops being proportional to gain x base current.

A good transistor can pull the collector down to 0.1V above the emitter or less.

The circuit shown isn't a standard switching configuration, its an emitter-follower.

The reason for posting this is to find out if that circuit is safe to use … eg I don’t want to end up supplying 5v to the due.

If not I’ll use a zener

MarkT:
The circuit shown isn't a standard switching configuration, its an emitter-follower.

And so it should maintain the emitter voltage at 0.6-0.7v below the base voltage.

cjdelphi:
I was curious about a transistors behavior when a higher voltage is placed on it’s base over the collector.
I’m unsure about this circuit, is this a safe way of shifting down (5v to 3) voltage?

You want the circuit on the left.
In your application, input would be that “5.14V”.
Replace D1 with another resistor, “R2”. such that VB is 3.9V.
(It’s the “voltage divider” thing - again.)
The resistor values will determine IB which will determine IOUT max.

Curiosity about “transistor behavior” aside, why not just get a “LDO”?