Electronics > Beginners
BJT/MOSFET as switch
exe:
--- Quote from: Moriambar on January 23, 2019, 07:53:38 pm ---Got it. I see now how it can be easier: pick a BJT and you hardly go wrong. Pick a MOSFET and you don't know what you picked.
--- End quote ---
My $0.02. I don't really want to get involved into discussion, but the statement above looks very wrong to me. You can't just "pick a bjt", you need to design a circuit around components with specific parameters. One can open an online catalog with parametric search to verify that there is more than one part number for bjts, and that's for a reason. There is nothing simple about bjts or fets unless someone already designed a circuit for you and gave exact part number that should work. It's a big mistake to think that to efficiently drive a bjt one just needs a single resistor. This is only true for very simple circuits. Hint: google "baker clamp", for example.
Driving with less than 1V sounds cool, but I personally never needed it. May be useful for amplifier, but for logic and switching not so much. Especially that bjts generally have bigger "on resistance" than power mosfets. I also doubt they are cheaper. And I doubt the price difference makes sense if you don't do volume production.
I left this post not to argue, but as an alternative opinion for other people who read this thread. But my best advice is just read a book. What was asked is common knowledge. I'd suggest at least read about Hfe, early effect, temperature drift, second breakdown, and trade-off between base current, saturation voltage, and speed. For fets read about Rds(on), gate charge, absolute maximum ratings, esd sensitivity, and derating. This will give data to make an educated decision for your specific application and will answer most of questions.
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