Base Resistor Selection BJT as a Switch

Quick and Simple base resistor selection for a BJT used as a switch.

[TheWebBot]

That's the right way to teach the complex topic in a simple way ... thanks a lot sir :)

[ahmadal-tarabeen]

This is so good explanation, short fast and straight forward!

[VS-qsfn]

Wow finally I figured it out. You teach perfectly for me thanx sir.

[xavier]

Honestly I spent hours on multiple sources to solve the learnings to this problem. This guy waltzes in, scribble and yells thoughts, 4:56 later, I have my answer finally, Thank you haha

[podunkpennsylvania]

Good clarifiation.I am a beginner. Thanks for your help

[doritos]

thank you very much! I am trying to make an 8-bit adder from transistors for my IT final paper but we didn’t even learn transistors or even LED’s in physics, this helped me very much

[fabienburguera]

Thank Lars, clear explanation. Love it.

[EhsanZia-Academi]

Thank you for this video with a great explanation. Just in practical situations Beta(saturation) = 10 NOT 200.

[RexxSchneider]

No. All manufacturers' data sheets specify saturation with a base current one-tenth of the collector current. You should drive the base with 0.1mA in this case, which calls for a 4.3K base resistor. The reason is the switching time being limited by the input capacitance, and that needs current to charge and discharge. A 2N3904, for example, specifies its delay time, rise time, storage time and fall time with an Ic=10mA and an Ib=1mA. You can't have fast switching without driving some current. In fact, some switching designs use a small capacitor in parallel with the base drive resistor to further improve the transient response.

[mohfa]

Thank you for your great videos...i have a questiin please : if we put around 40k Rb then the base current will increase, so will the current across CB also increase after multiplied by the gain?..Thank you

[mufeedco]

Thank you. It's great explanation and to the point.

[electronicman-ojvf]

Hello thank you very much for your explanation. but do you think a over drive factor (ODF) of about 2 for this matter is really enough?

[vkh]

I think that's IB(eos) = Ic(Sat)/beta
And Ib(Sat) should be equal to KIb(eos)
K being overdrive factor

[taurruth]

Great video. To bad it was so hard to find :)
One question: do I need a base resistor if I want to control transistor from output of an IC that gives 2V and 5mA on it's output?

[idiyerbill]

so thats what i was missing the load is important to determine the base resistor, the transistor doesnt act like a mechanical switch, anyways thank you so much for this great video

[alvinharyadi]

why 1000 ohms? All tutorials never explain how they come to decide on the resistance.

[makhanibhuyan]

*YOU DIDN'T TELL HOW TO CALCULATE THE GAIN?*---how tp calculate the gain and how got the value 200? What if the base voltage is same as the collector boltage? Is there a simple way to calculate that in that case?

[christianeriksson]

Great! I would have loved to see the datasheet of your transistor though, so at least part number would have been nice.

[otsutsukiboruto]

Thank you so much but could you what is the B = 200 again? i mean is it a resistance, a standard or what?

[richardmeborg]

Hi. I have a problem. Here I live in Africa, here is either difficult do get hold of DI-boxes for the music or they are way too expencive. So I dercided I will try to build them myself to sell them here.
I struggle also to get hold of metal boxes to build them in. A DI box is a Direct box which will isolate and create a better sound from the instrumnent through the mixer to the amp and to the speakers.
I Followed all the instruction I could find on internet. But still I got a buzz. And I building passive boxes there is only signals from mostly guitars going through.
Can it be because the boxes is all plastic or what can it be? Would it also help if I cut some metal pieces to cover the inside of the boxes to create a good grounding?