Such a Great video. Perfect presentation. You showed us the problem. Discussed the theory. Simulated a solution. Then tested your solution.... Perfect video workflow.
Thank you for enlightning us... I was fussing with BC547 / BC557, which were way to slow switching at 62.5kHz because of saturation... The (schottky) diode Base -> Collector was a gamechanger 🙂
Absolutely excellent video on the subject! 👍🏻 When you have to drive something like a mosfet, there is also something like a totem-pole circuit. Which can even switch faster as well as deliver a lot of current. Maybe it would be also interesting to see how these transistor circuits compare to switching with fets.
Thank you! I'm happy you enjoyed it! To be honest I noticed this turn off issue when working with the SMPS drivers, they ended up switch very slowly, so I had to limit my switching frequency to
OMG. i have faced a very bad experiment with this circuit before and it was such a disaster in my project and after many search and modification on board i found it won't work even with the modifications you mentioned in this video , simply because my collector voltage was to be 24v and you have to maintain a certain collector current to get better switching times and of course there was much power dissipated in the pull-up resistor connected at the collector. after all that trouble i used another ic and it can handle my 4MHz with no problems at all also without any external components. i really wanted to thank you to share this video with us and warn others from this trick.
Hi guys, when you download the model you need to ensure that string name inside is .SUBCKT BC817-25B 2 3 1 (like the video above) and not .SUBCKT BC817-25B 1 2 3 as in my case
Thank you for sharing this useful material. I want to suggest a topic for an upcoming video that I find interesting. "Array of transistors in parallel" to handle high currents. Simulate it and see its behavior with Ltspice. Again, thanks!!
Depending on the frequency at which you want it to act, its impedance needs to be smaller than the resistor over which it is placed; if you have a capacitor placed over a 1k resistor, and you want to "speed-up" signals above 1MHz, you can determine the capacitors impedance Xc=1/(2*pi*F*C), so a 1nF capacitor will have 159R at 1MHz, it will have a considerable impact, but the same capacitor at 1KHz has 159Kohm, so it does nothing.
I guess the Schottky diode across BC also works without the split base resistor? Or is a combination of both these nescesairy? (Also: commenting for the algorithm)
Hello Danny! I'm happy you enjoyed the video! In most cases, like with this video, .asc files I usually reserve for my supporters at Patreon as a way to thank them.
You mean in the base of the transistor? Well, one resistor is there to always limit the current, while the second one has a capacitor shunt - when a pulse is applied, the capacitor is shunting the second resistor, but after it charges, the second resistor reduces base current. The idea is to have a peak current during a transition and then a lower current after the transistor switches
@@FesZElectronics So u mean we need to select time constant of the of the input circuit in such a way that within input pulse width capacitor should charge fully.once it fully charged then it will act as a open circuit and second resistor will come into picture and it will reduce the base current. correct me if I am wrong.
Such a Great video. Perfect presentation. You showed us the problem. Discussed the theory. Simulated a solution. Then tested your solution.... Perfect video workflow.
Thank you for enlightning us...
I was fussing with BC547 / BC557, which were way to slow switching at 62.5kHz because of saturation...
The (schottky) diode Base -> Collector was a gamechanger 🙂
Very good video. I am not sure who you work for, but I hope your employer value your talent.
I'm happy you enjoy my videos! Thank you!
Thanks. Nice explanation.
This phenomenon has been bugging me for 4 days.
Finally found the solution.
Absolutely excellent video on the subject! 👍🏻
When you have to drive something like a mosfet, there is also something like a totem-pole circuit. Which can even switch faster as well as deliver a lot of current.
Maybe it would be also interesting to see how these transistor circuits compare to switching with fets.
Fantastic. I was testing transistor switching speed today and it was very poor. Now I know how to speed things up. Thank you Sir
A very concise explanation of how and why without the math is refreshing and enlightening. Please do more like this.
Very useful video with a good demonstration. You make some very good videos.
Thank you very much!
Great demonstration ....
Thank you! I'm happy you enjoyed it! To be honest I noticed this turn off issue when working with the SMPS drivers, they ended up switch very slowly, so I had to limit my switching frequency to
I just love this simulation hardware iterations to understand/improve the circuits. Thanks for sharing.
OMG. i have faced a very bad experiment with this circuit before and it was such a disaster in my project and after many search and modification on board i found it won't work even with the modifications you mentioned in this video , simply because my collector voltage was to be 24v and you have to maintain a certain collector current to get better switching times and of course there was much power dissipated in the pull-up resistor connected at the collector.
after all that trouble i used another ic and it can handle my 4MHz with no problems at all also without any external components.
i really wanted to thank you to share this video with us and warn others from this trick.
I'm new to all of this and I'm glad I found this channel!
Hi guys, when you download the model you need to ensure that string name inside is .SUBCKT BC817-25B 2 3 1 (like the video above) and not .SUBCKT BC817-25B 1 2 3 as in my case
Thanks for the tutorial on switching delay of bjt.🙏👍
Thank you so much 😊. Please keep doing videos like this. One question, are you working for any company?
Great video, very helpful!
Thank you for sharing this useful material. I want to suggest a topic for an upcoming video that I find interesting. "Array of transistors in parallel" to handle high currents. Simulate it and see its behavior with Ltspice. Again, thanks!!
Hello Diego! Interesting topic, I will keep it in mind! Thanks for the suggestion!
@@FesZElectronics Great..!! thank you...!! (congratulations on the style of the back wall. It looks very good! ja!)
What symbol is in the video thumbnail?
It's shottky transistor
Superb as always!
If i may ask, how did you determine the necessary value for the speed-up capacitor? I cant seem to find anything about it.
Depending on the frequency at which you want it to act, its impedance needs to be smaller than the resistor over which it is placed; if you have a capacitor placed over a 1k resistor, and you want to "speed-up" signals above 1MHz, you can determine the capacitors impedance Xc=1/(2*pi*F*C), so a 1nF capacitor will have 159R at 1MHz, it will have a considerable impact, but the same capacitor at 1KHz has 159Kohm, so it does nothing.
So BC549 that have 100MHz max, with this circuit can give 20MHh max?
great video thank you!!!!
I guess the Schottky diode across BC also works without the split base resistor? Or is a combination of both these nescesairy?
(Also: commenting for the algorithm)
Thanks for the great video, can we get the .asc file?
Hello Danny! I'm happy you enjoyed the video! In most cases, like with this video, .asc files I usually reserve for my supporters at Patreon as a way to thank them.
Very useful information in very effective method.
Can you do the same with a phototransistor? For example, the pc817. It is that they are also very slow for switching
Check out: 2N2369 and BSV52
they are true BJT switching transistors.
Thanks bro
Great Bro,
Can you please tell me which computer simulation software you are used in this circuit simulation video?
Hello! I use LTspice in all my videos. Its a free simulation software
@@FesZElectronics
Thanks bro...
That's very helpful :)
Great video 👍 , I like the new wallpaper also
Thanks! I wanted to try some sound proofing and came across the hexagons! They are so soooft :D
What is the simulation software you are using?
I use LTspice in all my videos. I also have a few tutorials for the program.
@@FesZElectronics thank you for your quick response!
oh, man, you are awesome
Very good content. Exellent channel!
I did not understand the purpose of using split resistor.could u please explain little bit.
You mean in the base of the transistor? Well, one resistor is there to always limit the current, while the second one has a capacitor shunt - when a pulse is applied, the capacitor is shunting the second resistor, but after it charges, the second resistor reduces base current. The idea is to have a peak current during a transition and then a lower current after the transistor switches
@@FesZElectronics So u mean we need to select time constant of the of the input circuit in such a way that within input pulse width capacitor should charge fully.once it fully charged then it will act as a open circuit and second resistor will come into picture and it will reduce the base current. correct me if I am wrong.
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