Simple driver circuit would it work

[numberonekiwi]

I believe by using a standard pnp transistor with a zener diode would give you a fairly accurate voltage regulator I think that zeners are available as 2.7 and 3.3 v which would just leave the resistor of around 19~24 ohm depending on which zener was used

Would this work in practice ? if it does cost of components < $1.00

 

[rog8811]

You may need to look at the current capabilities of the transistor, I have used this circuit in the past for non critical items like cassete players (if you don't know what that is go to your local museum) that required a large heatsinked transistor (TO-52 case??) they will not be as stable as a proper regulated circuit as far as I can remember....

Regards rog8811

 

[Benm]

A zener + transistor voltage source works okay, with output voltage roughly 0.6 volts below zener voltage. With proper bias to the zener, these are reasonably stable with varying loads or input voltages.

However, they are voltage sources, not current sources, hence not really good for driving laser diodes at all. You can make a current source with only 2 transistors and 2 resistors, and those work like a charm too.