I need to know what formulas or set of calculations would be used to figure out the base resistor and load resistors when hooking up a darlington pair as my datasheet for the ds2003 does not provide a hfe. The chip is 7 darlington pairs, and I am hooking it up to be controlled by my micro controller, to drive leds. If I know the current I need for my led to be saturated, how would I know what base resistor value I would need to put on the inputs to keep the base current under 25mA
Essentially I want to know what formulas are used or what is the common practice for designing such a circuit (led driver)
Single transistor calculations seem to be well published and I always have a hfe to work with but this is missing from the datasheet for these darlington drivers.