Using an NPN transistor to drive multiple LEDs （使用一个NPN型晶体管驱动多个发光二极管）.pdf

Using an NPN transistor to drive multiple LEDs from a PIC microcontroller output ht t p :/ / pic p roj ect s .o rg .u k V is the power supply voltage V is the power supply voltage Supply voltage V V V is the LED forward voltage V V V is the LED forward voltage f f n is the number of LEDs in series If is the LED forward current If is the LED forward current Rled = V - Vf Rled = V - ( n x Vf ) If Vf If Vf Vf Vf To PIC 1K To PIC 1K To PIC 1K Driving a single LED Connecting multiple LEDs in series The configuration above can be used when the number of LEDs in series would be The supply voltage should be a regulated DC source. greater than the supply voltage. Try to work When connecting multiple LEDs in series, the number of LEDs must be such that the sum wit