IC to NPN transistor
- From: Digitmode@xxxxxxxxx
- Date: 21 Oct 2006 23:34:37 -0700
Hey I need some help calculating some resister values, I cant seem to
find the formula anywhere. I'm trying to trigger a NPN transistor to
switch on a set of leds when my IC's output goes HIGH. Heres my values:
NPN transistor:
Typical Hfe - 200
Max Vce - 30v
Ic - 800mA
Power dissipation - 1.8w
IC:
Lowoutput - 8mA, 0.35v
Highoutput - 0.4mA, 3.5v
Power Source - 5v
Leds:
4.5v x 6
20mA x 6
What I need to happen is when the output goes high is to turns on 6
leds (parralle) operating at 20ma each from a 9 volts source. I already
know I need a 39 ohm resistor for the leds, what I really need to know
is how to calculate the resistor value I need between the IC and the
transistor.
.
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