Sorry to dig this thread out of the grave but it seemed useful and It's 22 years since I last really delved into proper electronics so my discreet circuit skills are very rusty.
I am going to use one of these
http://pdf.datasheetcatalog.com/datasheet/toshiba/3392.pdf
to drive a bunch of LED's
I believe my total current draw will be 1.5A
My supply voltage will be 12V
Going on the calculation above and trying to find the figures from the data sheet does this seem correct.
Required Collector Current 1.5A
Base Signal Voltage 5v
Voltage Drop Vbe(sat) 1.2v -- from data sheet
Beta (Hfe) 40 -- not sure taken from data sheet???
Calculated Base resistor 101Ohms So go for a 110Ohm Standard resistor.
Am I on the money or barking up the wrong Tree?
Cheers
TT