Hi,
I was trying to use an NPN transistor as a high side driver - the collector connected to 5V and the emitter connected to my load and the other side of the load to ground. What I found was that when the base was high, a much smaller than expected current would flow.
Then I moved the transistor so that it went from 5V to load to transistor collector, and then transistor emitter to ground and would much more current would flow.
I guess I thought it would be the same either way, but is an NPN transistor capable of switching much more current from near ground to ground than it is from near 5V to slightly lower than 5V using the same amount of base current?
If this is true, then are NPN transistors really only good for a low side driver, emitter to ground. And them PNP transistors would really only be good for a high side driver, collector to 5V, emitter to load?
Thanks,
Alan
I was trying to use an NPN transistor as a high side driver - the collector connected to 5V and the emitter connected to my load and the other side of the load to ground. What I found was that when the base was high, a much smaller than expected current would flow.
Then I moved the transistor so that it went from 5V to load to transistor collector, and then transistor emitter to ground and would much more current would flow.
I guess I thought it would be the same either way, but is an NPN transistor capable of switching much more current from near ground to ground than it is from near 5V to slightly lower than 5V using the same amount of base current?
If this is true, then are NPN transistors really only good for a low side driver, emitter to ground. And them PNP transistors would really only be good for a high side driver, collector to 5V, emitter to load?
Thanks,
Alan