Hey guys, i was just wondering if I had a 8.45V power source that provides about 90mA what would you recommend as the best way to get the current up to at least 550mA? Thanks in advance!

 

Assuming you want 8.45V out, you need a different power source.

 

1) AC or DC? If the former, get a 6.1:1 transformer and you'll get about 1.4 V at approximately 550mA. If you need 8.45V, then you can't do it with just what you have,

2) Get a more powerful power source.

 

DC, but all right that's all I guess.

 

Oh what if I use a transistor

 

Oh what if I use a transistor

At 100% efficiency, power in = power out. Your power source, in round numbers, is 0.85W. At 500mA, you could get a volt or so...

 

At 100% efficiency, power in = power out. Your power source, in round numbers, is 0.85W. At 500mA, you could get a volt or so...

Oh I see

 

You just need to know the math to understand what you can/can't get..

Volts x Amps = Watts
so
8.5V x .09A = .765watts of power available


Now Watts / Amps = Volts
so
.765w/.55a=1.4V

So assuming 100% efficiency (and you won't get that in the real world) as stated above you could supply 550mA BUT that would only be at 1.4V

This chart shows you all the ways to use volts/amps/resistance/wattage to figure out each other.
http://www.ohmslawcalculator.com/ohms-law-wheel