How to choose the right MOSFET?

Question

I am looking to use a MOSFET to switch a linear actuator on and off. There's nothing else on the circuit, just the switch and the actuator (and a Raspberry Pi to control the switch.)

The actuator takes 7.8V to engage and draws 1.26A of current. There's no datasheet for the actuator so those are all of the numbers I have.

• How do I pick the right MOSFET?
• What are important variables to consider?
• Is there some sort of website that I can use to filter through all of the options based on those variables?

Answer 1

Picking the right Mosfet

Theare are several basic tutorial with the topic "Using MOSFET as a Switch", for example this one or this.

The minimum parameters you should consider are:

• V_DSMAX: Choose it higher than the supply voltage. 60 V mosfets are commonly available.
• V_{gs th}: Control voltage. If you are using a RPI, the outputs are 3,3 V so pick something that can turn ON the mosfet. Check charts V_DS Vs I_D parametric depending on V_gs
• R_{DS on}: The smaller, the lower the conduction loses.
• Add a freewheeling diode to the actuator in order to protect the mosfet.

Websites to filter

You can perform a parametric search on any electronics component dealer: Mouser, newark, digikey...

Example With that in mind, a couple of examples: Mosfets: PMV37ENEAR (SMD) or IRFZ24NPBF (Through hole) and for diode 1N4001 will be enough. Asuming you are not doing PWM.

^{simulate this circuit – Schematic created using CircuitLab}