I have been repairing a plug in power supply for my led illuminated magnifier. The output rectifier diode had cooked. As a temporary measure I put a 1N4007 diode in to check if there was basic functioning in the high voltage side. I was shocked at how hot the diode got yet only passing 360mA or so. It wasn't until a friend pointed out the slow recovery time was the cause that the penny dropped. I harvested an ES1J off a dead phone charger - a fast recovery rectifier and everything worked fine. Thank you for your very helpful demonstration.

I was having trouble with my zero-crossing detector because of this. We always have to learn the hard way that these are semi-conductors! Semi means they only do part of what you think they should do. Thanks for taking the time to explain this to us all.

Good as always. I'm glad you showed a 914 and a schottky too.

Understood what is diode reverse recovery time from this video. Spend enough time in my academic books, but was not able to understand the concept. Thanks for the video.

Thank you for all the time that you spend making these videos. I appreciate it!

The behavior of the schottky diode is interesting, perhaps that could be a future subject? Another great video!

So well explained that I have now understood much more about diodes than ever before in one go! Amazing your introduction Alan!!!!

thank you for the video! it is very helpful. I especially like how you introduces things on paper and experimental results !!!

Alan, your brilliance is inspiring. Looking forward to your next lesson

Another good one Alan! There is so much stuff that I don't know. Thanks to you, I know a bit more each time I watch one of these.

Thanks! You always have the best EE tutorial videos!

Thanks man! You making us smarter with every video. I have few random old diodes from old SMPS, will be interesting to see what recovery time they have

Can't thank you enough for showing what goes on Inside components!

nice, clean fixture and excellent explanation

Another extremely interesting and well presented video presentation. Thanks Alan.

Beauty of analog circuit is time resistant. Keep on going revealing this beauty to all of us! I'm becoming to be addicted :)

Thanks a lot for very clear explanation. After going through lot of articles I did not get things cleared. But you did it very nicely. Thanks for your good work. Wish you the best.

Oh,,I know nothing about this. Thank you for this great deep understanding lessons you are showing to us. It's very helpful.

Thanks for the video! It needs to be emphasized that this test method is valid only for small-signal diodes. High current rectifiers (1A - 3A average If) can't be properly tested at low currents like this. A 1N4007 can measure nearly the same as a 200nS fast recovery rectifier with 10 - 20mA. It's only when current is increased above 100mA or so that the difference in speed becomes apparent.

Thank you, ive been repairing equipment for years but never really looked close at the diode reverse recovery, smashing video :-D

Excellent. Thank you. Catching up on some of your older videos.

In one of my projects (a big power supply) I have a bridge rectifier consisting of 4 huge diodes in a bridge format.... Although it is of no worry to me the ouput after the regulator does have a very low level (a few mV) of commutation noise from the diodes. Once again a very well presented video, always food for thought...

Outstanding video as always. Thank you!

Thanks Alan, very timely as I was just sorting a parts bin of PIN diodes and came across some VERY old ones I'd gotten from Hamtronics years ago that I don't have a data sheet for (neither did they). At least now I can compare these to others that I have the data sheets for and at least get a feel for how they match up to known units. 73 - Dino KL0S

Watched again after a few yrs. , and learned even more ;) Thanks again

Great job mate. Really good explanation. Thumbs UP

awesome explanation and examples!

Great video. Love how you present the theory followed by a practical demonstration.

Thank you sir, was confused what trr is, after watching the video my concepts are now clear.

Awesome video!! thanks for sharing!

Great video, I had never really thought about how to measure reverse recovery time.

Excellent video, keep them coming.

Whenever there is a topic I'm looking for more info on in electronics I first go to w2aew, this is beautiful and stuff that I don't even have in my textbooks

Thank you for the clear explanation 😊

Very professional, Great presentations

I am glad I found your channel!

Thank you for your clear explaining!!

A great clip again. Now that I think of it, that is why we can use varactors in VCOs with higher AC voltage than reverse DC bias of varactors. Of course, here you are talking about forward bias charge storage, in varactors it is reverse bias charge storage. (ie. diffusion capacitance vs. depletion capacitance) However, in my opinion the best way to see if you have a pin diode or not is to figure out its doping profile. You can do this by incrementally biasing the diode, and measuring its capacitance and relating it to its doping profile. If you want to do this you should bias the diode from just below to turn on voltage and slowly decrease the bias voltage up about about 1/3 of reverse breakdown voltage measuring capacitance at each step and inferring the doping, and create a complete doping profile.

Great as always.

Thank you for your great explanation.

thank you very much this video crarified some doubts that i had on my lesson great video

Thanks Alan! Excellent!

Dear sir u got my respect ... from india .. tnx a lot....

Very interesting and educative

Great video, thanks!

hello from the other side of the earth no words will show my thankfulness i have watched and learned a lot from most of your videos i need a video also about MOSFET false turn on due to the dv/dt i will repeat this comment in videos i have seen this morning in my country so you can them also this is the only support i have for you for now

I was hoping that you would plug in a Drift Step Recovery Diode at the end of your video.Once, I had an old Russian PN rectifier diode, that was so poorly manufactured that the boundary between the P and N region was very diffused and that made it an excellent DSRD. It was snapping off in under 1ns with 200A of reverse current flowing through it which allowed me to generate kW nanopulses with it. Great stuff!

Alan, please, do a video about the Jim Williams pulse generator.

Great video.

Thanks for the video.

very very awesome....thanks bro

I love ur videos!

Great video. Thank you again for sharing. Quick question; does the probe's capacitive loading have any effect on the waveform ?

Great Video Thanks.

Interesting practice again! A question. I would know how you made your PCBs. Thanks for all

very helpful... make more videos please on smps

Thank you

Thank you 👍

Thanks

Could you do a video on non ohmic devices and how they can effect circuit design and troubleshooting?

Have you done something similar with LEDs? I seem to remember recombination time is effected by the amount of light falling on the junction. I wonder if that would allow for mixing using 2 LEDs facing each other.

Very interesting thanks for sharing the knowledge. You know what would be a good idea for video. How dc to ac inverter works inside in the electronics. A solar inverter for axample. Have a good day. keep making videos like this one.

I pulled some pieces out of a power supply, including a big rectifier. I thought it would be a good practice to put my signal generator and scope to the test. I noticed this phenomenon and wondered what the heck was going on!

Great video! Can you do a video on the physics of Schottky diodes? If they are not pn junctions, what are they?

Thank you for this video! It is great as always! I have a question. When you change the bias conditions by adding more voltage to the positive side of the wave, that affects how long it takes for the diode to recovery from the reverse bias - I can reproduce that offsetting my waveform to the positive side. I performed a test using the 50ohm impedance generator and a 100ohm resistor to represent load. I measure with the 1x scope probes. If I change that 100 ohm resistor to a 1k, I thought it should affect the recovery time, but it doesn't seem to be the case. It seems like the higher the resistor, the higher is the negative spike but it does not affect the recovery time. Would you please help me understand why?

I just noticed the EEVBLOG sticker on your workbench. What is the story? Thank you for the exceptional work in explaining "simple" concepts to us. I keep re-seeing your episodes

Alan, what type of parasitic capacitance do you think is between your pins and does in have much effect on the measurement? Maybe 1-2 pf?

can we built a constant current source given the voltage source we have is AC and it's constant. we need to vary the impedance and still the constant please answer am stuck.

Can you show spectrum of signal at 10:05? Is it possible to make sampling phase detector at home with 1n4148? Isn't that good idea for next video :) Only problem as I can see is that SRD produce spikes with sin. signal while 1n4148 need bipolar square.

I had much hassle with a UF4007 at work, they massively change their Trr and the current spike with temperature, too!

That is quite a dramatic demonstration of "reverse recovery" time for various types of diodes. Before watching your video, reverse recovery time was just a number on the spec sheet that was respected, but seeing it "on the screen' really brought the meaning home. Thank you. WA9KZY.

Great video! Do you have a video about double diodes? I see lots of them in my junk box, usually from old switching power supplies. I used to think they were transistors.... I still don't know what they're for.

Hi have you tried an OA79 point contact Ge diode? I have a bunch of them and since it is very old, I could not find data sheet spec on timing.

@7:39 The transition from -1v to 1v seems to produce some overshoot and ringing. Can you conjecture what causes this? Maybe PN junction capacitance plus stray inductance in your setup? @8:10 Given a fixed forward bias voltage, I would guess that the area under the reverse recovery curve is constant. So increasing the reverse voltage level increases the amplitude and decreases the duration. Thanks for the quality videos.

Could standard rectifiers then be used in RF applications? Like the classic 1N4004, of which I have a bunch? Or is the junction capacitance going to cause them to conduct RF through them even while reverse biased? 8:01 is the "area under the curve" conserved? it almost looks so. If so wouldn't it be more sensible to specify reverse recovery time instead as a charge instead of a time? Is there any phenomenon that may cause a diode to be "slow" to enter forward bias? Like for the use of clamping a signal between supply rails on an H bridge?

Outside of this junction capacitance and reverse recovery time, what are other limiting factors to device switching speed? Are there any limitations to how fast a diode conducts when flipping from reverse bias conditions to forward bias conditions? Great video BTW!

I saw a small scope model sitting on the function generator. Where to buy it, please? Thank you.

Hi Alan again, as said excellent video, can you explain Schottky diodes at some point too?

At about 8:42 when you placed the "power diode" with the 1N4001, you stated that it (the 1N4001) had a "longer" Trr. On the scope it looked like the Trr was actually a bit shorter: Am I mistaken? Thanks again for the great videos!

Alan, thanks for the video, so the flat area prior to the exponential is the diode storage time and the exp time the transient time and the 2 added together give us the total transient recovery time.

Could you explain the theory behind why the recovery time is shorter when you apply a greater reverse bias? Wouldnt that enhance the space charge region making it take longer to recover? Also what is with the lack of recovery going from positive to negative bias? Thanks!

how did you generate this perfect square input signal - probably from a proper signal generator? How could you easily generate a fast slope good square signal without a decent signal generator? Is a NE555-timer good enough for this? I dont think so - so what could you use in a very simple aproach?

Hello ,diode bars can be recovered?

I will thumb up first, then watch your video

Nice video. So I take it the reason why PIN are used is that they have a much lower reversed bias capacitance than rectifier diodes, since both have long recovery times?

Can you help me to design RF to DC conversion circuit. Which book to refer ?

Can you test 200 and 600 V shotky diodes and MUR860?

Hi, when it is said that voltage source is applied to a diode, what does that mean ? 1.whether higher energies are supplied to already existing charge carriers inside the diode ? or 2. whether high energy electrons are supplied by voltage source ?

I guess this is the same phenomenon that prevents saturated BJTs from turning off quickly because of the forward biased collector-base junction. Am I right? Or am I in the right place to be corrected? :)

So does this mean that fly back diodes won't be fully doing there task on relays and motors? Should I be using a capacitor as well?

If the diode isn't initially forward biased and is instantly reverse biased, does this concept still apply? For example, if there is a negative pulse that goes from 0 to -1V, will it initially allow reverse current to flow or will it block the reverse current?

Is this same effect happening to transistors? Is there such a thing? I was watching a guy on youtube building his own CPU from transistors and integrated circuits on breadboards. He had a knob so he could manually adjust the clock speed. He said something that If the clock speed is too high, the program he run on the cpu didn't give the correct answer (he was adding some numbers). Is this limitation due to the reverse recovery time in the transistor? Or if this is not the problem, why does the clock speed can't be higher than a certain value? Do you have any recommendation on what should I read?

Seems a bit like how gate charge on a FET constrains it's switching time

👍

This is square wave. Did you try to see the impact of Trr on sine waves, if others haven't asked (can't search comments)?

I'm confused is the reverse recovery time the reverse bias leakage current of the diode? because I thought it was the same thing the reverse recovery time is how much the diodes reverse bias leakage current value is. The diode reverse recovery time increases more by how much the diodes leakage current is?

How can you measure the diodes leakage current and reverse loss while applying an AC signal at different frequencies? If I put an ammeter current meter in series with the diode it will only measure the current but how can I measure the leakage current and reverse loss? Does Zener diodes have a recovery time?

I'm trying to measure reverse recovery time of Schottky Diode with Oscilloscope. Is it possible for me to measuring it without making that kind of PCB board? Like just putting resistor series with diode. Do I have to buy current probe?

GREAT VIDEO. However I have NEVER (in decades) found what P.I.N. stands for?????????

Interesting, the power diode shown actually recovery slower than the PIN diode.