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beesher
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Homework Statement
an npn transistor is used to drive a constant current I through three ‘white’ LEDs, connected in series. If the required current value is I = 25 mA, and the current-gain of the transistor is β = 300, find the value of the resistor R, giving your answer to 3 significant figures. You may assume for the operating conditions specified that the base-emitter voltage of the transistor is 600mV, and that its saturation voltage is 150mV.
I should point out that the base of the transistor is connected to a voltage divider, with a resistor of 10k above a resistor R.
Homework Equations
Base Current = [tex]\frac{collector current}{gain}[/tex]
The Attempt at a Solution
Hi guys looking for a bit of help on a past paper for my instrumentation class.
In this problem, I've tried to find the base current by dividing 25 by 300, and I'm a bit stumped as to the next step. Do i simply need to to divide the base current by the saturation voltage, or is that completely wrong?