Hi,
I have a project which controls an "array" of LEDs using a microcontroller. Because the MCU can't output nearly enough current, I use transistors to amplify the current.
Currently I use 2222's (NPN) to switch between either letting current flow out of a group of LEDs' cathodes, or not. And I use 327's (PNP) to switch between either letting current flow into a group of LEDs' anodes, or not.
This works great, but as my project is battery powered, I want to switch to use different transistors which perform the same function, but with the smallest voltage drop possible, to reduce power wastage. (I'm using a switching regulator for just the LEDs' supply voltage, so if I can reduce this, I'd get longer battery life.)
Unfortunately, my knowledge of transistors is quite basic. Looking on Digi-Key, they don't list transistor voltage drop as a spec, so I'm not quite sure where to start. I'm embarrassed to say it, but I don't really yet understand why 2222's and 327's are commonly considered a good choice for controlling LEDs any more than any other transistor.
I need each NPN transistor to supply up to 350mA peak, 35mA continuous. And I need each PNP to supply 100mA continuous.
Does anyone have any recommendations, or pointers in terms of what other specs I should be looking out for?
I have a project which controls an "array" of LEDs using a microcontroller. Because the MCU can't output nearly enough current, I use transistors to amplify the current.
Currently I use 2222's (NPN) to switch between either letting current flow out of a group of LEDs' cathodes, or not. And I use 327's (PNP) to switch between either letting current flow into a group of LEDs' anodes, or not.
This works great, but as my project is battery powered, I want to switch to use different transistors which perform the same function, but with the smallest voltage drop possible, to reduce power wastage. (I'm using a switching regulator for just the LEDs' supply voltage, so if I can reduce this, I'd get longer battery life.)
Unfortunately, my knowledge of transistors is quite basic. Looking on Digi-Key, they don't list transistor voltage drop as a spec, so I'm not quite sure where to start. I'm embarrassed to say it, but I don't really yet understand why 2222's and 327's are commonly considered a good choice for controlling LEDs any more than any other transistor.
I need each NPN transistor to supply up to 350mA peak, 35mA continuous. And I need each PNP to supply 100mA continuous.
Does anyone have any recommendations, or pointers in terms of what other specs I should be looking out for?