Perfect Base Resistor Selection: Mastering Transistors
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- Опубліковано 2 бер 2024
- Unlock the secrets of transistor circuits with our comprehensive guide! In this video, we delve deep into the crucial role of base resistors in transistor circuits. From understanding the fundamentals to mastering advanced techniques, you'll learn why selecting the right base resistor is essential for optimal performance and reliability. Join us as we explore simplified and advanced methods, backed by real-world examples and datasheet analysis. Whether you're a beginner or an experienced hobbyist, this video will empower you to confidently choose the perfect base resistor for your projects. Don't miss out - watch now and level up your electronics skills!
Transistor Selection Video:
• How to select best tra...
Thanks for the methodical and deep dive into the selection which was explained very well.
You're very welcome! Your positive feedback made me feel awesome 😃
Thank you for describing the topic so simply and clearly. Excellent job :)✌
Thank you too for watching 😊
I absolutely love this channel.
I love you too ❤️😃
Please continue making videos like these👍
I will do my best to keep making new videos.
@@elewizard thank you sir.
@@elewizardthere's many of us that need help with understanding how to make a transistor turn a motor off and on with a trigger coil.
We build pulse motors...
Could you please make a video.
Turning a transistor on off with a trigger coil.
Thank you for the video, Master! I now understand why resistor should be present at the base of transistor. Keep up the good work! Greetings from Philippines!
Thank you so much! I'm glad you enjoyed it 😊
Very clear explanation I hope you keep on going with your series.
Thanks, I will do my best to create more content 👍
I don't care about your pronunciation ,your content is very convincing and helpful
Thank you ❤
Thank you! 😃
I am working on improving my accent 🙃
@@elewizard It's fine. Enthusiasm, and excitement can't be faked.
Does make me wonder what the life expectancy of your bread boards are. 😄
Awesome content!
Grateful for your kindness - the 20SEK Super Thanks means a lot! ❤️❤️❤️
With the motor example, a microcontroller can't source 200mA on a pin so be careful about that!
Thank you for explanation! It is very usfull
Thank you for watching ❤️
@@elewizard Thank you! Keep going!
Great video! Thank you!
Keep watching bro
Thanks!
Hi husain, Grateful for the AED250 Super Thanks, you're amazing! ❤️
I like the videos that you make they're really insightful
Glad you think so 😊
Great video. Thanks
Thank you for watching
Very informative and professional... Thank you.
You are very welcome. Glad the video was helpful 👍
Great and valuable video
Thank you amir, glad you liked the video ❤️
Very Well explained,thank you.
Glad it was helpful!
My simple method is based on the hfe classes of the device used. For the BC547 there are hfe classes A, B and C available. Usually I work with the class B, which has a minimum hfe of 200. The Vbe_sat goes from 0.7 to 0.9 V. So I consider a safe saturation region at hfe = 100 and Vbe = 0.8 V. The higher the base control voltage is the less important becomes the actual Vbe_sat.
So when I need to drive 10 mA from a base control voltage of 5 V I can expect a base current of 0.1 mA and calculate a base resistor of 42 kOhm. The closest E-12 resistor is 39 kOhm. But I have also no problem to use resistors down to 10 kOhm in this case, dependent on my personal stock. Circuit design for saturated BJT is no rocket science.
For the control of motor currents of multiple Amperes power BJTs are not the best solution because of their relatively low hfe. Also microcontrollers cannot usually drive the required base currents. You can use Darlington or Sziklai configurations to increase hfe. But the best way is the use of (logic level) MOSFETs.
It was a very useful video, thanks a lot
Glad it was helpful!😃
I am expecting more videos from you because your style of teaching is super (from Sri lanka)
I'm so happy you liked the video!
Thanks for watching and for the encouraging comment!❤️
I am planning to make more videos 👍
Well done! You covered all of the important points accurately. The only place you need to take care is using the graphs in the datasheets, because they are _typical_ values. Those will tell you the most likely values of a parameter, but sometimes (e.g. power dissipation) you must consider _worst case_ values. For the BC547, a base current of 0.3mA will _typically_ result in saturation with a collector current of 30mA, but it's not guaranteed. It is better in this case to forget the graphs and look in the datasheet for the maximum value of Vce(sat) and the conditions pertaining. You'll find it's 250mV at Ic=10mA and 600mV at Ic=100mA, in both cases with an hFE=20. So you use hFE=20, which means Ib=1.5mA when Ic=30mA and you'll always guarantee saturation.
Why did he choose hfe as 10 @10:45 and hfe as 10 @13:02 , can't we choose hfe as 100 or 200 to minimize base current . Can we choose base current as 100 to 400 uA and still get 300mA IC to drive 5 leds (5mm leds , pwm pulse current 70mA ) in parallel. Vcc is 4V
Yes, exactly. Thank you for sharing your knowledge ❤️
I have mentioned that the base resistor which is calculated is the threshold value separating active and saturation regions. As I mentioned, we have to select a value lower than the threshold to make sure that the transistor will remain saturated!
By the way, I am glad that you personally, confirm the information of this video😊
@@Blue.star1 Because most transistors are tested by manufacturers with an hFE=10 when looking at saturation voltage. There are a few high gain transistors that are exceptions to that, and as it happens the BC547 is one of them. Check the datasheet for common transistors like 2N2222 or 2N3904 or the BC637 family, etc. and you'll always find the maximum value for Vce(sat) is quoted with the base current one-tenth of the collector current.
You can't choose higher gains than the manufacturers specify because they only guarantee that the transistor is in saturation when the base is overdriven. You might get away with 1mA base current when drawing 300mA collector current, or you might not and your transistor overheats and fails, but unless you're prepared to test every transistor in every circuit you build, you can't design like that. When you're looking at possible failure modes, you have to design for the worst case, not the typical one.
@@Blue.star1 To ensure a 2N2222 saturates at 350mA collector current, the manufacturers datasheet will guarantee saturation with 35mA base current. If you want to try it with just 1mA base current, you can, but you have to test it and accept the likelihood that the transistor might not be saturated and may not have enough drive to deliver 350mA. Not being in saturation probably isn't crucial because with a duty cycle of just 5% and the metal can version able to take 500mW continuously (more with a heatsink), it will probably not overheat.
I would expect the bae-emitter junction to require around 0.7V when drawing 1mA, so you would need a base resistor of (4V - 0.7V) / 1mA = 3.3K.
Three more things: why are you worried about drawing more than 1mA into the bas when you are using 350mA to light the LEDs? If the LED power supply is separate, then have you considered running the LEDs in series, using a higher voltage supply, and taking just 70mA? If the low base current is an absolute necessity, then you should revise your choice of transistor to a Darlington like the TIP120/140 family or use a logic-level mosfet like the IRLZ44 or similar.
It is a very much useful topic , but never made a video by any other youtubers... Thank you so much sir to clearing this very useful topic❤❤❤❤
I am really grateful for your kind words my friend 😃
It's comments like yours that inspires me to keep going ❤️
@@elewizard your videos are always full of knowledge... That's why I'm a big fan of your videos
بسیار عاالی استاد
Thank you for the compliment. Keep watching ❤️
this was fascinating, as always, i have been immersed in all the maths of late, really understanding β, etc. despite learning about this stuff for a year I only just applied myself to really _understanding_ ohms law. i used to kinda cheat-220O for LED, 1k for BJT base, and just wing it. but i now have a much deeper understanding of transistors and the maths.
i know i always mention laser drivers, but i find them endlessly fascinating. as i learn more i keep making better laser drivers, my latest one uses a 4013 for latching switch, which drives a 520n 'fet, which turns on a lm338 which delivers 1.7A to my laser diode. it is all on perfboard-for which i found your soldering tips very helpful.
Si kind of you dude 😃
I am glad that my videos are helpful for you ❤️
I hope you find the best way to driver the laser diode 😉
@@elewizardhonestly i have gained so much from your tutelage, my bench book has pages and pages of notes from you. all the uses of capacitors etc are numbered and written in my book. you really have changed my life by increasing my understanding. when i open a SMPS, or a knackered LED bulb, your uses of components are always in my mind. sharing knowledge is what humans are all about, and it is the most wonderful thing. thank you so much for the time you have taken to make these vids. i have copied most of the things you have done in videos on breadboard too. cheers mucker.
Another super helpful video. Thank you from Toronto.
Suggestion: How about a video on how hot components can get safely (datasheet)? Can I use a thermistor and microcontroller in a project to monitor the temperature, of say a mosfet, an reduce the PWM duty cycle if it is too hot, or is that not reliable to safeguard against over heating? If it is a reasonable thing, how do I do that, glue the thermistor onto the mosfet? Do I need a heat sink on the mosfet? How do I determine that (where in the datasheet)? How big should the heat sink be and is there a way to determine that (do heat sinks have a rating for heat disipation)? Does the enclosure need vents to help disipate heat for my project? Maybe just a bigger enclosure so there is more space foe the heat?
Thank you dude for the compliment 👍
I noted your suggested subjects👌
I hope you could make a video about oscilloscopes, basics, how to use etc,. Cheers,.
It is in my todo list 👍 however there are plenty of other videos before that
Amazing explaination. I have a question. I have an input that is pulled high at 12 volts through a 1M resistor. However when this input pulled low by a switch I need it to switch on a transitor that will output 0 volts as i have to switch an active low logic gate that works on 5 volts. What is the best way to do this? Thanks
You want to limit current through the base emitter junction.
It is interesting calculation base resistor in exampel with the relay. It is much hiegher then in previuse exemple. Do you think that drop voltage on transistor doesn't change?
Surely It will change 👍
Yeah, this is why I don't use bjts unless needed, mosfets are way better as switches, and any gate resistor between 10-33ohm is fine.
Also diode/current source model is way better for beginners than trying to explain Vce, and tell them its a current controlled current source.
Thank you for sharing your thoughts, it is much appreciated 👍
Do you not need a pull down resistor for turning it off quickly when Ic is removed?
There are plenty of considerations that are not covered in this video. I tried to keep the content understandable for wide range of viewers 👍
MCU usually have internal current limiting trasistors...
Eureka!
Wow 😃
Great, I want to make a power supply about 30volt and 5A ,how to drive a 3055 transistor with 4558 opamp? . Make a video about making a CC and CV power supply.please ..
I have plenty of subject in my list, but I will consider making a video on your desired subject 👍
💖💖💖💖
❤️❤️❤️❤️❤️❤️
No need for a base resistor if the load is on the Emitter. The hfe divided by the emitter current will be the base current. Been driving QI lamps for years by connecting them between earth and the emitter. Collector goes straight to V as does the base when turned on.
The configuration that you are talking about is called common-collector. Yes, in that case maybe a base resistor is not very important, but some other considerations and limitations will come into play.
more resistor wattage more amps capacity of resistor?
Yes, it is some how true 👍
The more the wattage, the more a resistor can pass at the same voltage
Can't mosfets be used instead? I am just learning electronics, and really like MOSFETs, like IRFZ44N, i need to build a few voltsge dependant switches to shut off at ,28.5-29v, to work as a voltage regulator for a alternator, the outputneeds to supply a unspecified voltage until the output reached ,28.8v after rectified, i need about 6-8 of these I'd like to fit on a 50x 80mm board, be adjustable to upward of 65v DC. The gate side need tobbe capable of handling this voltage , are you interested in designing a circuit? I need help, i was thinking of just using a zener diode and resistors to try making this regulator circuit. I can really use professional advice..
Yes, either mosfets or BJTs can be used as a switch for a DC load. Anyway, subject of this video is to cover the calculations needed to find the base resistor value. I think using just a zener is not a good idea, you need a reference voltage that is reliable, the voltage generated by a zener diode is not much reliable. You can use reference voltage generator ICs and an op-amp to make the desired voltage.
However there are plenty of other methods to complete the task you are going to do.
A voltage regulator on an alternator does not shut off. It increases or decreases current supplied to the rotor based upon a voltage comparison. It operates as a big linear voltage regulator. When voltage goes higher than battery max it turns current down to zero, and when voltage goes below battery min it provides maximum current. In between these points the current turns up and down.
Mr. @jamest.5001, you specified that you are a beginner in electronics. You want to create a circuit that uses an alternator and produces a voltage of up to 65 volts at the output. You must know that you are subject to some risks.
1. Making some assemblies with Arduino, for example, which works at 5V and is powered by a 1 or 2 Ampere source with current limitation is not dangerous for beginners. In case of a mistake, the Arduino board can be damaged, an LED, transistor or a sensor can be destroyed.
2. Voltages higher than 24V are dangerous and voltage of 65V DC can kill you!!!
3. The current that an alternator can provide can reach 30 - 50 Amps or more. So a short-circuit or overload at the output can cause fires if the circuit is not provided with appropriate fuses. So it can set your car or house on fire if you don't have overcurrent protection in the schematic.
4. Some schematics found on the internet are not tested enough or may have design mistakes, wrong wiring diagram or PCB with routing errors.
5. I recommend that before actually making the installation, you check the scheme using a simulation software such as LT Spice, OrCAD, Simulink, Proteus, Texas Instruments TINA, NI Multisim, etc. The design of electronic circuits in specialized companies, by engineers, has a mandatory circuit simulation stage to discover design or calculation errors before practical implementation.
6. Thus you don't waste time making a circuit that is not tested or that does not work. You can modify (or recalculate) component values and observe the behavior of the circuit without damaging the parts.
7. For alternator simulation, three independent Voltage AC sources are used which have the initial phase shift of V1=0 degrees, V2=120 degrees, V3=240 degrees. The excitation coil can be simulated by a resistance because it is supplied with direct current.
Good luck and don't put your life or property in danger.
I obviously cannot speak for everybody, but I really appreciate your videos, but I would like to see you do one thing. PLEASE slow down, or better yet, show the math SLOWER. You go through it so fast, that I cannot follow, and just go to a different video. I know that most people that are trying to work in electronics are quicker, but seriously, if they ARE quicker, they probably don't need your instructions.
Thank you.
Thank you so much for your feedback. I thought that viewers can pause the video if they need more time to analyze the calculations 👍
Very good teaching, very good teacher. But here again the problem with the unclear pronunciation.
Yes، I am working on improving my English skills everyday 👍
Thanks brother
Your welcome dude, keep watching ❤️