MOSFET Bootstrapping 

This is an excellent explanation. I realy like the way you give context (NMOS Low-side and PMOS High-side) before explaining the problem (RDS is too high with PMOS High-side, but NMOS High-side circuit dont work) to finish with the solution (Cap. + diode bootstrap). Thank you very much.

This is how tutorials should be presented. Excellent.

Well organized, well presented, clear and concise. Thank you for an excellent tutorial!

I whacked the subscription bell soon after you said you use automotive spec in many designs. The automotive industry has ramped up its tech over the decades, and now it allows hobbyist a lesser expensive route to quality and robust electronics where previously there was only expensive aircraft silicon. With the advent of electric vehicles, that has only widened the selection and ubiquity of very interesting electronics. I’m happy the cost bar has lowered!

I can't say how grateful I am for this video. Thank you very much!

Thank you. For the past hour I couldn't tell how the capacitor and voltage source acted in series until you motioned with your pencil.

Very good video, I like your videos a lot. I recently learned that there are some optocoupler that are driver mosfet. Like the TLP591 - DC Input, Photovoltaic Output. They are not cheap, but the voltage in Gate is independent of the PSU of the load, which makes it immune to voltage drops and other problems.

finally, you make it clean and clearer, appreciate it.

Thank you for this turorial. Bootstrap driving of mosfets is now much clearer thanks to you.

Finally someone that explained exactly how a "boot-strapping" circuit works 😍😍

Thanks, this subject was playing in my head today

Your videos are the best!! Your explanations are very clear and entertaining

thank you so much, I've been struggling to understand bootstrap and finally you have made me understand it very clearly

Sweet! A use for all those cheap low Rs n-channel mosfets . I used a open collector output comparator to drive the bootstrap. Worked great well up into ultra sonic frequency.

Great idea bud. Very simple and probably very functional even in long period cycles if one use good quality, low leakage parts.

Awesome video, this is what I was looking for :D

I FINALLY get it now. Thank you for this wonderful explanation.

I like mosfets and i like bootstrapping, now I know how to do both at the same time!

Very practical and Very useful circuit idea. Thanks.

Congratulations from Brazil.

many many thanks, now i understand whats going on with bootstrapping, theres alot of indepth videos and very dry explanations out there, however yours was very interesting and in the short time perfectly understandable in comparison to the hours in class of trying to understand the subject matter, keep up the good work. Top, thanks once again.

I love you. Ty for saving my presentation in university

You just earned yourself another subscriber :D Excellent explanation. Thank you :)

ohhhhh... that's why my solenoids were being weird with my optocouplers.. thanks so much for this clear explanation.

It is very powerful circuit and cheap. I test it, work like charm!. Thanks you very much. I used boost converter but it is costly and design is not very good for small package. I used it for bicopter, I will upload soon.

Thanks a lot for video! it opened a new window for me.

That was a great video. Thanks !!

Great video!! Thank you for uploaded it.

Good video. Thanks for this idea.

this is excellent design! the explanation is better!!

TNX 4 the upload 73 N8AUM

thank you for making this video. i see you have few views and thats a shame cause it helped me so much. keep it up! I wan't MORE!

Thanks. I like this idea. I'd love to see more hints like this. While tearing apart old consumer electronics P-Channel MOSFETs and Power PNP BJTs seem to be extremely rare. In fact the only place I know I will find a P-Channel MOSFET (without ordering anything) is on lithium battery protection PCBs, typically in a SOT-8 package. Even the cheapest Chinese adjustable power supply kits, sold for around $5 use a power NPN BJT. I'd like to see you explain the different configurations to avoid the use of power P-Ch/PNP devices. It's handy information to have in those situations where I want to build something now and can salvage a part instead of ordering something and waiting a week or more ;) BTW, if we are switching any power MOSFET with a stable Gate voltage, how easy/accurate is it to use the voltage drop of the Rds resistance in place of a shunt to measure the current? Would I need to measure the Rds resistance value of the actual part used? What's my potential measurement resolution? -Jake

You saved my energy

Excellent. Thank you!

Interesting circuit nice refresher for an old timer

Thanks for the info... As I understand it correct, I can use 4 LL N-channel fets for an h-Bridge on 24V. As log as I feed the top ones 29V to switch using Optocouplers or so.... thank you!

Thanks a lot man, great video, great explanation

Very nice explanation , thank you !

Excellent. Thank you very much.

Great video!!

Thank you, best explanation

Best explanation, appreciate

Nice video, thanks.

Great vid.

great explanation. thank you soo much

nice, I learnt a lot

the diode and cap solution, is that equal to a charge pump circuit? cause u doubled the 12 Volts?

My eyes was messing with me! I was scrolling down, and im like what the heck is Boost trapping! Ha-ha

Awesome Explanation. 5 stars ★★★★★

Thanks so much, great video! Can you recommend a good p-channel mosfet for high side switching, that can be driven by logic, and control 3.3-5 v? Want to interface to arduino.

Quite brilliant.

If I were to use an n channel depletion type mosfet instead of enhancement, can I turn this circuit from 'normally closed' to 'normally open'? Also, can I control that npn transistor with a raspberry without killing it? What were to happen If I used an electrolytic cap instead of the cap used in this video? Thanks! Really handy video.

Brilliant. Explained exactly as you need the information. P channels may be easier but I want to avoid them because of the high SD r. PS. I like the IRF1407. Their "F" but run OK off arduino. Also, I assume its going to work OK for brushless motor? Thanks!

Can i use Gate drive Transformer instead of GDIc ? What will be the disadvantages ? I wanna use it for driving Half bridge of Class D Amplifier?

Thanks so much, great video! ,This mosfet IRF1405 and Will this circuit you explain work with 24V

Hello, and thanks for the excellent tutorial. Quick question: I've seen you say multiple times in the comments that this setup is not intended for high-frequency applications, and that one should use an integrated circuit for such a case. What is the advantage of using an IC over switching out components for lower-valued ones that could support a higher frequency?

I have a question , on the first example with the N channel you had a resistor going to ground (pulling down the gate ). can I put the resistor to vcc instead of ground ? So it would be pulling high unless the signal goes low , and the load would be allways turn on unless the signal turn it off

This is great! Thanks for sharing! What would be the approach if I'm looking to leverage the pwm of an arduino and a high side n-channel mosfet to control 12V LEDs? Should I build a mosfet driver?

Excellent👍👏.

perfectly explained

is there a way to control the high side of a circuit with 2 n channel mosfets controlled with a pin of an arduino

Very very very very very informative 🔥🔥

Tnks for tutorial,, but if the voltage more than 12volt, example from automotive battery ? Need change mosfet

7:53 you can increase holding on time by using a 1n400x diode instead of 1n4148. 1n400x has lower leakage. Learned that from Bob Pease. Also use non-electrolytic cap.

Thanks a lot.

Does it invert the signal?

Thank you

Thank you. Didn't know about this technique. Can you make a video about different types of mosfets, their main characteristics and circuits?

thanks, usefull video 👍

3:11 how this can be done if both mos are n type in Half bridge construction ?? In which upper mosfet ground is floating .

@6:00 I would add a bleeding resistor with value depending on the loading and wiring conditions. On other side we may use a BJT transistor to connect the bleeding resistor to the cap to discharge it once the PWM is tunrned OFF. I was thinking about where else can we insert the bleeding resister! I need to build this circuit and try it for further testing.

To drive a 1700V mosfet, I assume the same circuit will work if the components meets the voltage ratings, capacitor, BJT, diode and resistors to say 1500V

excellent job , this has clearedup an issue I was struggling to accept , have you gone on from this vide to discuss charge pumps which I also need an additional awareness of

Awesome thanks!

If one were to increase the value of the cap will the duty cycle increase for the on state of the Fet?

Why does the collector ground at the beginning? And if it is ground, the node after 1n4148 a ground also, isn’t it? Then how the capacitor charges up?

cant pwm be used to keep the capacitor charged?

So would this circuit work for PWM as long as it didn't hit 100% Duty cycle? If I'm understanding it correctly, it should

Nice video. Don't you feel the leakage current via the 10K resistor would be more than the leakage current via the diode?

Be aware, that the circuit will not work with any PWM or several Khz signal. This works only for very low frequencies from Arduino. To get the same effect, you need to use a boost converter to give double as much voltages to the gate which let the MOSFET to switch ON totally.

Is the purpose of the 1k resistor on the gate to limit the current flowing off the gate when switching it off? Is this necessary? Or am I completely misunderstanding?

I can't get this to work! The waveform at my mosfet gate looks sawtooth instead of square, any idea what I'm doing wrong?

Please can 311V be the input to the entire circuit? Plus the bootstrap circuit

There are also p-channel MOSFETs with considerably lower Rdson like the IRF4905 with 20 mOhm or even the IXTP140P05T with just 9 mOhm. The p-channel MOSFETs for higher voltages have mainly higher values like the 500 V IXTP10P50P with 1 Ohm.

Hello! is it important the frequency that you got in the pwm signal? Because I calculated the RC time constant is 22ms. Does this work well with a high frequency?

Excellent

I am new. Doesn’t the RDS on .8ohm issue go away after a few ms so we could use a P channel mosfet in continuous mode and avoid the capacitor draining/switch off?

What is the lower and higher limit of the frequency that this works? I used with an arduino pwm .. but the voltage over the gate doesn't rise to the 24V. Which means that the frequency is not suitable for your circuit. I don't know how to make it works.

Hello a query from Argentina: according to the data sheet of the irf1405 the Gate-to-Source Voltage is 20volts, how is it that it does not break if you put 24volts in the gate? very cool video!!!

Ciss is the input capacitance, gate to source and gate to drain (Ciss=Cgd+Cgs)

Thank you 0033mer!

How would i add a mosfet driver

can u do a similar video but using a dedicated gate driver chip

Hi again, I want to understand how the bootstrap capacitor works. Kindly tell me about it.

QUESTION: the datasheet for IRF1405 says that Vgs is ± 20V. So now with bootstrapping Vgs becomes +24V exceeding the maximum allowed. Why is this not damaging your MOSFET? What if my Vcc is 48V. Then Vgs would be 96V. Would this not destroy my MOSFET? If not then I need to understand what is the real meaning behind Vgs. Thank you.

You said that the gate to source voltage will be 24v so it means if I bootstrap the irfz44n with same ckt and power input then it will fail since the max gate voltage for irfz44n is ±20v??

nice thanks

Can this work with 400v across MOSFET in 3 phase

This circuit can be using a ignition coil???