How and which transistor to turn on or off a VCC rail (sim800l)

Hi, i burn a 2n2222 traying to do exactly this

i was try with a tip122 in the gnd rail, the problem is the virtual serial connection, have to be the same gnd, so thats is why need to be in vcc.

Thanks

You need a PNP transistor or a p-channel MOSFET to switch Vcc. Pulling the base/gate low will turn on the device and supply power to the circuit.

You can get away with switching a 3.7V circuit from a 5V one as here, but not the other way round without
adding a level-shifter. If you had to switch a 12V circuit this way an NPN level shifter would typically be
employed to drive the PNP/p-chan device.

i found this Pchannel:

the Datasheets and in Aliexpress

so, if i use it i have to add it a step up buck converter? how can i know what resistor use for digital pin?

I like this P channel:
http://ww1.microchip.com/downloads/en/DeviceDoc/VP2206%20E082313.pdf
images.png

756E6C:
I like this P channel:
http://ww1.microchip.com/downloads/en/DeviceDoc/VP2206%20E082313.pdf
images.png

without a resistor? =O

MOSFETS don't need resistors. It's one of the reasons why they are more popular.

That circuit will work only if the voltage of the microcontroller ("PIC") supply voltage is equal to or higher than the voltage at (+). Also choose a logic-level MOSFET, which will turn on properly with only 5V - conventional MOSFETs require 10V.

so, the solution is a logic level mosfet chennel P, but can not find it on aliexpress, how can i know if is a logic level looking the datasheets? :sunglasses: do you know a mosfet like that on aliexpress?

Sorry, I don't deal with aliexpress or E-Bay for components, I usually use Digi-Key or Mouser.

Usually a datasheet will say logic-level, but the key value is the Vgs quoted in the on-resistance entry,
ie something like "Rds(on) = 0.05 ohm at Vgs=-4.5V"

The -4.5V means its ok to work from logic levels (ie 5V plus or minus losses), and for a p-channel the
Vgs is negative (its the voltage between gate and source, not between source and gate!) If it only
gives on-resistances for 10V (or -10V for p-channel) of gate drive, its not logic level.

Logic level p-FETs aren't the commonest kind of device, remember a PNP transistor might be easy to
source (no pun intended).

What current does the device being switched need BTW?

MarkT:
Usually a datasheet will say logic-level, but the key value is the Vgs quoted in the on-resistance entry,
ie something like "Rds(on) = 0.05 ohm at Vgs=-4.5V"

The -4.5V means its ok to work from logic levels (ie 5V plus or minus losses), and for a p-channel the
Vgs is negative (its the voltage between gate and source, not between source and gate!) If it only
gives on-resistances for 10V (or -10V for p-channel) of gate drive, its not logic level.

Logic level p-FETs aren't the commonest kind of device, remember a PNP transistor might be easy to
source (no pun intended).

What current does the device being switched need BTW?

2 amps as peak power

756E6C:
I like this P channel:
http://ww1.microchip.com/downloads/en/DeviceDoc/VP2206%20E082313.pdf
images.png

You may like it, but its inappropriate for 2A, as the on-resistance is over an ohm.

A 10k resistor is needed between gate and Arduino 5V rail to hold the device off during
reset, and a logic-level p-FET of 0.05 ohms or lower would be good, 0.1 ohms at a pinch.