In my Arduino 3.3V project I have a problem shutting down a GPS module.
When it "sleeps" with a command, it comsumes 2mA which is way too much for my project. To my understanding I have to build a high side FET to switch the module ON/OFF.
Do I have to use a BC212B (PNP) transistor? Why is the current negative?
I read this problem for a high side switch:
"In that case, it'd be impossible to turn the switch off because VB (connecting to the control pin) would always be less than VE."
Since LiPo is 3.3V-4.2V and to my knowledge the pins of feather are ~3.3V this is a problem. Right? So, I do I need a MOSFET or an NPN like BC546?
I tried two diagrams, they are right?
Low side switch (I think not recommended)
High side switch (recommended but unusable?)
My setup Feather 32u4 (max 10mA per pin) 3.3V
GPS module needs 20-25ma (let's assume 30mA) but in the future I may need to use a more hungry module ~50mA.
I want low power level like this guy.
My idea is to feed the transistor (BC549) from lipo battery 3.3V - 4.2V and to control the transistor with an output pin of the Feather.
If I understood the basic from transistors, the more current in base, the more current in output (device). I have to supply 0.1mA to have 50mA on output of transistor (worst case: cold), right?
In BC557B PNP specs the numbers are positive.
Can I power ON/OFF my GPS module with a transistor?
What resistor to base for low consumption for 30mA scenario and 50mA scenario? 3.3K (30mA) and 1.1K (50mA)?
I read that I have losses with a transistor of 0.2V (or 0.6V?), so when my battery goes to 3.4 volts my module will it be problematic? I think it needs 3.3 volts not sure about 3V.
UPDATE: added all the components