Trying to add led lighting to my rc car. Ive averaged the pwm, got my comparator working, fed that into the base of a 2n3904, emitter to ground, collecter to the led cathode, anode to positive rail. Yay led lights. Added more led's in series, no more light. Well figured that was wrong, so I tied all the cathodes together and set all the anodes to their own positive voltage. Yay they all light, but for all of about 10 seconds or so. Im using a 9v battery for the source of the comparator, and the led's. With two bright white led's, two red led's, and eight green led's a new 9v battery lasted like I said about 10 seconds if that. I an using a fighre of about 20mA for each led, sincei dont have datasheets for them, I figured a 9v should last longer.