What Power Supply Voltage?

[Greeny009]

once ive designed a circuit how do i determine what voltage power supply would be suitable?

[peps1]

Ohm's Law
(Most people start with the voltage, and make the circuit around it)

[R.G.]

once ive designed a circuit how do i determine what voltage power supply would be suitable?

It is in general backwards to do that in the way you've described, designing a circuit, then picking a suitable power supply.

Rather, the power supply voltage is nearly always a given starting point, and you make the circuit work within the available power supply.