Or using just a simple complementary transistor pair that can output 500mA.
I didn't take my time to draw the complete circuit.
Fact is that treadstarter haven't provided that much information. If output consumption is to be 50mA over long time, then PWM could be a better choice.
Oh, I just get it. Question above is equivocal. I assumed that a 2-3 volt signal should be amplified to 4-5 volts, where a power supply is already avaiable.
However, you assumed (i guess) the 2-3 volts IS the only powersource and it's neccesary to boost it to 4-5V.
Treadstarter must make that clear to make it possible to answer it :roll: