I describe how to design a simple transistor circuit that will allow microcontrollers or other small signal sources to control low-power actuators such as solenoid valves, motors, etc.…...more
When the transistor turns off, current flowing through the coil will cause a voltage rise on the collector. If the voltage rise is high enough to turn on the diode, current will flow through the diode and limit the voltage at the collector. The problem is that the diode cannot turn on instantly. It takes time for the diode to start flowing current. The capacitor smooths out the rising voltage, and gives time for the diode to start conducting.
I've never watched a video that was as informative and clear. Your explanations are complete without getting overly complicated. Thank you so much for making these.
I wasted weeks learning all you say in here, which I could have learned in ~20 minutes. Great video. Please add more tags to it, so you rate higher in search results.
This video should be shown to everybody starting electronics... No talk of doping and PN junctions, show them this first so that they get a picture of what they are doing.. Too many electronics courses start at the microscopic level.
For 30 years I've seen explanations of how to use a transistor and never "gotten" it. Bravo this is spectacular. The best explanation of a bipolar transistor I have ever seen in any medium.
@2:54 Your description of the circuit symbols for NPN vs PNP BJTs is so ridiculously simple and intuitive
@7:00 So THAT'S what hFE is used for with BJTs!
This whole video is so informative it's helped me to make tons of sense of how BJTs work. You, sir, are a genius. <3
Clear and well-presented. Amazingly, this circuit was pretty much the same as when I started studying electronics back in 1975, including the 2222 transistor! So for you younger students, the techniques outlined in this video will practically never become obsolete. We tend to think that the world is run on low-voltage, low-current technology (e.g. microprocessors, microcontrollers). But at some point real work requires higher voltages and/or higher currents, so studying transistor control circuits, like the one presented here, is very valuable knowledge.
Good Tutorial. Thank you for that. Just another thing: You have to consider the power dissipation of the transistor itself, due to the voltage drops across it. taking the numbers (0.2Volts and 56mA), you can say that the transistor dissipates like 11mW of power, which is quite low for that circuit, but if you have a larger current and also a larger voltage drops on the transistor, you could damage your transistor if you don't attach it to a proper heatsink.
Thank you, thank you, thank you, for mentioning the 0.7 volt drop across the base-emitter junction, when calculating the base resistor. I see many people forgetting to subtract that 0.7 volts. When using 5 volts to drive the base, forgetting that 0.7 volt drop across the base-emitter junction will create a 14% error, when calculating the base resistor. That’s more than enough to prevent the transistor from switching properly.
Also, for the beginners, when he talks about the “clamping diode”, it’s worth mentioning that it goes by many different names. You’ll hear terms such as, “kickback diode”, “buck diode”, “flyback diode”, etc. They are just different names, for the same diode. Use a good diode, as well. One of the most popular silicon diodes, which I recommend, is the 1N4007. Actually, the MOST common one is the 1N4001, but it’s rated for much lower voltage. The difference in price, between the 1N4001 and 1N4007 is so negligible, that it’s worth just buying 1N4007’s. That way, you’ll be covered for any voltage that you’re likely to come across. It also provides an extra safety margin. In a “clamping” application, a failed diode will typically fail ‘shorted’, which will burn up your switching transistor, as well. It’s definitely worth spending an extra penny, for the better diode.
I'm pretty sure this is the best introduction to how to practically use transistors and explanation of their essentials of how they work I've ever seen.
Why couldn't I have had you as my electrical theory teacher. What I learned in 21 minutes with you took me weeks with my teacher....and I probably still did not quite digest and assimilate it well enough. Thank you for your tutorials and lectures. You are educating the world.
Just what I needed - Transistors are a simple yet madding concept that pushed me to look for a tutorial to get back to basics. Found exactly what I was looking for!
I think i watched hundred of videos on the same subject.
This is the first time that i see someone explaining every single step, all others always take those for granted.
And abole all i appreciated the first part, when he described the several choices (possible components to use). All the designers make tutorials and never clear why they use a particular component among others and indeed they must know the reason (again take that for graanted).
I congratulate and thank you.
