LED Driver - with two NPN transistors

260

02:48:35

Uses a transistor base-emitter junction as a reference voltage. The supply voltage is varied between 10 and 14 Volts, typical of automotive lead acid batteries and charging systems, but the 100mA LED current is constant to 0.6% 

Most current variation is correlated to the Zener diode voltage variation, providing bias current. 

published 6 years ago

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