# solar panel + N channel mosfet on the high side

#### Bogdan.m

Joined Apr 20, 2019
57
What is the easiest way to drive an N channel mosfet on the high side, so the ground is 0V, i tried using a charge pump to create the extra voltage, but my arduino goes crazy when i use it.

#### Irving

Joined Jan 30, 2016
3,435
Show us the circuit and explain what you are trying to achieve.

#### jpanhalt

Joined Jan 18, 2008
11,087

#### Irving

Joined Jan 30, 2016
3,435
Yes, I would say the same but wanted to see what the issue was first...

#### Bogdan.m

Joined Apr 20, 2019
57
i have a mosfet(actually 4) connected source to battery, in order to turn it on to charge from solar panel i need a higher voltage than the battery no ? this is my issue, i have no circuit design for this, i put things on my breadboard as i need it. I started to make a pcb design for this, maybe it helps. Would using a P channel mosfet save me from extra work with driving an N channel ? and how would i drive it ?

#### jpanhalt

Joined Jan 18, 2008
11,087
The difference between P and N channel can be simplified to: P-channel source current; N-channel sink current.

To turn an N-channel on, voltage on its gate must exceed voltage at its source by whatever is shown for Vgs , say 10 volts. With an N-channel sourcing current, that translates to a gate voltage that much higher than the supply voltage, because there is almost no voltage drop across the mosfet.

For P-channel, one just pulls the gate low to turn them on.

Yes, your circuit should be simpler if you use a P-channel device to provide current to the load.

#### Irving

Joined Jan 30, 2016
3,435
Yes, P-channel much simpler. NMOS left, PMOS right
With NMOS you have to get the gate volts Vgs at least Vth (MOSFET threshold voltage) above the source which rises to Vcc when switched on, therefore you need the bootstrap voltage to be > Vth + 0.5v above Vcc.

NMOS is best used when the load is on the Vcc side, and the MOSFET source is grounded.

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#### Bogdan.m

Joined Apr 20, 2019
57
So i could use P channel mosfet and an inverting driver like the tc4426 and be done with it ?

#### Solar Mike

Joined Apr 26, 2018
33
just use one of those 1 watt 12-12volt isolated 4 pin PCB power supplies to generate your gate voltage supply, and use an opto-isolated gate driver for your mosfet. Depending on the expected charge current, N-Chan mosfets have less loss due to their much lower on resistance.

You may find using a single mosfet will allow the battery to self discharge into the PV panel via the mosfets internal diode at night, unless blocking diode is in circuit, or you use 2 mosfets connected source to source.

Cheers
Mike