MOSFETs and How to Use Them | AddOhms #11
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange answerers point people to it as a beginner-friendly introduction to using MOSFETs as switches, especially when replacing a BJT for higher-current loads.
Recommended by 1 people across 1 different months, 2018 to 2020.
What it is
A short beginner tutorial from AddOhms, part 2 of a series that follows an episode on BJTs, explaining how MOSFETs work as switches. It covers the practical basics of using them with an Arduino, BeagleBone or Raspberry Pi, including how to work out whether a heat sink is needed.
What people said
Strong rec Nettle Creek · 2018-02 · Electrical Engineering Stack Exchange · on “NPN-transistor to switch 3.3V”
Personally, I would use a MOSFET in this application since you are only using it as a switch and you want to keep the voltage drop across the device (MOSFET) as low as possible. Whether or not to use a pull-down resistor on the gate will depend on what device you are using to drive the MOSFET. If you build the circuit, and the MOSFET won’t turn off or acts erratically, use a pull-down resistor. Here is a great MOSFET tutorial video for beginners. The MOSFET used in the video (Fairchild FQP30N06L) is very common and is one of the MOSFETs that I use the most for Arduino and Raspberry Pi output circuits where I have to control larger devices. (I buy them in bulk!) Pay attention to the part of t
Cites AJ_Smoothie · 2019-01 · Electrical Engineering Stack Exchange · on “How to switch a 12V DC (3A) Motor with a 3.3V signal?”
You fried your little 2N2222A transistor because you exceeded it's maximum current ratings! If you take a peek into the datasheet [LINK] , it shows the absolute maximum current. [LINK] Okay so the datasheet claims 800mA, but that's assuming you are able to keep the device cooled to T(A), which you can see is 25C (room temp). That's a whole another story though. In general, with a 2n2222A, you don't want to switch currents more than 500mA. Let's find you a better component to switch your motor on and off (or varying speeds!). A quick search on Adafruit reveals the IRLB8721 [LINK] . Behold the N-Channel MOSFET! If we take a peek inside its datasheet [LINK] , we can see that it will switch a ma
Cites Michael Jennings · 2020-01 · Electrical Engineering Stack Exchange · on “Darlington as CB”
For high current loads. BJTs are a current-controlled device, so one might not provide enough current amplification. This is called the beta value and is normally around 100-300 for general purpose transistors The base current is being amplified and projected through the collector to the emitter (in NPN). If it's common base, the current is the same through both transistors. Stacking the base of the second transistor to the emitter of the first one provides amplification in the 1000s Good point, these are expensive! Alternatives are MOSFETs [this video] which are voltage controlled and can handle high currents. NPN, PNP and Szikial pair (push pull amplifier) [LINK] These are generally labelled in