I have a uC (Arduino Mini) powered from 2xAA battery pack. The Mini display some data on a circuit with a MAX7219 + 2x7segments 4 digits led (a total of 8 numbers).
Because it is powered from battery (and for learning) I want to switch off the load totally when Arduino sleeps, and power on only when needed.
So, this is the very basic schematic (U1 the uC and U3 the load)
I know that for the high side switch I need a PNP, and with a PNP I need mantain GPIO HIGH (right?). But if Arduino sleeps, how it can mantain high?
But, other this question, I'm tryng to study transistors and FET/Mosfet from some months, but I find they very difficult to learn.
Please, can you help me with:
1) Know if circuit is right (R1 for limit base)
2) How can I select a transistor? What I need to check in datasheet?
3) I have some part available, are there some part available for my goal? (Mix of NPN, PNP, FET and Mosfet:
N CHANNEL MOSFET
P CHANNEL MOSFET
N CHANNEL JFET