I've got a backlit LCD with the following specs, If=300ma, Vf=4.2V-4.5V. My power supply is 5V and I'd like to keep it that way. Now if I use a simple 2.7ohm resistor to limit current everything works fine. The problem I'm having is what's the proper way to switch the backlight on and off.
The transistors I've tried don't seem to work because the Vce(sat) (seems to be around >=.6V for all the ones I have) is high enough to affect the current (and taking worst case scenario of 4.5 Vf the .6 V Vce(sat) would make it not work at all).
I think the same type of situation would happen with a MOSFET, though someone please correct me if I'm wrong.
So my question is what's the best way to tackle switching this load on/off? Do I bump up the source Voltage to 6 or more V (in this case that resistor starts getting more and more wasteful)? Do I look for some exotic darlington transistor with a really low Vce(sat)?
I apologize in advance if this is a stupid question, I probably should've paid more attention in those EE classes. :oops: