this is an old video but i just came across it. i have only used FETs in SMPS and never tried them in the linear mode. Very interesting and informative. just yesterday i watched ur other one dissipating 400 Watts but didnot pay much attention to it. now i am going back to it so i can learn more about linear loads. thanks for sharing.
@KerryWongBlog6 жыл бұрын
Thanks! I recently used the other one to test the battery bank I built and was able to push it even further and dissipating more than 1kW into the load.
@RicardoPenders2 жыл бұрын
I had an old plasma tv that broke down so I decided to pull all useful parts from the PCB's and I found a couple big IGBT's, some smaller ones and a few MOSFETS. So I made a DC load using just one little MOSFET which is a TO-247 package, marking on the MOSFET is: ST W13NK60Z, max. 600V, max RDS(on), 0.55 ohm, max 13A and max power dissipation is 150W. I've put it in a box and used a tiny fan from an old broken Xbox that someone gave me to recycle, it's one that blows the air sideways. And for the heatsink I took the biggest one I had from an old computer power supply, so it is not very big but it's the one with the thickest aluminum plate and the most fins, taking this into account I know I have to be very conservative with the maximum power I can push through the MOSFET. So nothing is optimized for what I'm using it for and I've pushed this little MOSFET pretty hard and tested it a substantial amount of time at the highest I dared to go. What do you think? I hooked up my 70V DC transformer, rectifier and capacitor bank that I made also from old stuff, big audio transformer that can handle quite a lot on the 70V output, it also has a 50V and 25V output after rectification which is pretty nice to have for testing stuff that can handle higher voltages as the usual bench top power supplies. Well, I pushed 70V and 0.8A at first and it didn't get too hot with that so I pushed it a little bit further to 0.9A and it was still fine, keeping my eyes on the voltage level and amperes drawn watching it stabilize to my surprise, so I pushed it to the maximum I thought was still safe which is 1A... That's a 70W constant current load that I left running for about 15 or 20 minutes to see how hot it gets. It's pretty toasty in that little box with that small heatsink but I didn't smell anything funny so I consider the test a success. Before I used the MOSFET that I mentioned above, I tested a couple other MOSFETs that I took from the plasma tv PCB's, two different types that looked pretty good on the datasheets but I've blown those to smithereens pretty quick which was a lot of fun to see the magic smoke come out, sadly I didn't see any flames or sparks. However, I never thought that the MOSFET that I'm using now would be as strong as it is, able to push it far beyond what I thought was possible. I've watched quite a few videos from you and used your ideas for my own DC load so thanks for sharing your knowledge online, I appreciate it very much. Best regards, Ricardo Penders.
@fjs11116 ай бұрын
Excellent video Kerry, thank you for your excellent work.
@patrickpafarnis57982 ай бұрын
Am not very well versed and already of age but have been fiddling with a simple controller for a house fan for a long time. If you want to control it with a triac then faza cut-off takes place. It works but makes the motor hum. The only solution I've found is with a variac, but that's a big device to control a (a)synchronous motor. More than once I have tried to do this with MOSFETs, but these need control, which is not so easy.
@cdiperformanceparts43644 жыл бұрын
Nice project and I just wanted to asked about the mosfet. It looks like you have all three leg of the mosfet shorted and soldered togther.
@intheshell35ify Жыл бұрын
This guy might have saved my life.
@stevieboi612 жыл бұрын
im newbie but you explain very well. thankyou for sharing.
@pentachronic6 жыл бұрын
Emitter degeneration resistor (source degeneration) will help solve the tempco problem. Resistor will increase in voltage to counter the VGS voltage vs current. It's related to Gm during linear part of plot. Solves thermal runaway IIRC.
@voltlog7 жыл бұрын
Nice video! I didn't know these linear region mosfet existed. This also explains why I might of killed allot of mosfets with my dummy load experiments.
@steverobbins48726 жыл бұрын
Don't listen to this guy. He doesn't know what he's talking about.
@fellpower10 ай бұрын
This MOSFET is a BEAST ;)
@RoB04447 жыл бұрын
Nice video. Definitely worth watching. I am a little confused as far as how the electronic load and the DUT (the power supply in this case) are grounded. Where is the common ground in your circuit. Is it at the shunt resistor? How is this not shorting?
@KerryWongBlog7 жыл бұрын
Thanks Rob, the ground of the circuit is tied to the PCB towards the bottom of the heatsink (where all the black alligator clips are). The power supply to the electronic load is actually floating. Hope it helps.
@gerliansilvasilva8084 Жыл бұрын
Hello Kerry, I am wanting to build an adjustable electronic load capable of draining up to 250 Amperes, I initially build one using 32 IRFP260N mosfets but I believe they will not support for a long time, I am using 4 LM324 comparator based control module doing gate control of the mosfets, As a Shunt resistor each mosfet has a 0.10r 5W resistor, My question is, Is it possible to use 8 mosfets IXTK82N25P to obtain a good current drain? Each control module controls 4 mosfets and would it be necessary to change each Shunt resistor of 0.10r for a smaller value, for example, 0.05r? Would it be necessary to do this or would I have much more efficiency just changing the IRFP260N mosfets for the IXTK82N25P linear mosfets?
Жыл бұрын
Well information. I suscribed. But one thing: 1st term is Y-axis and 2nd term is x-axis, not reverse. So, Vgs vs Ids is wrong. The correct way is Y-axis vs X-axis or Ids vs Vgs.
@aswathisivasankar2651 Жыл бұрын
Sir.. You know how to make dc electronic load with pic microcontroller?
@andymouse4 жыл бұрын
Excellent vid, learnt ton's...cheers !
@noslidemais4 ай бұрын
@beeelectronics76224 жыл бұрын
Thanks !
@4833504F7 жыл бұрын
thanks, I didn't know such devices exist.
@KerryWongBlog7 жыл бұрын
You are welcome!
@antoniomonteiro12032 жыл бұрын
The connections on the metal board are not clear. Everything seems to be in short circuit which obviously is not the case. I would like to see how drain, gate and source are isolated as well as the two copper plates. Apart from that, it is a good video about the subject.
@KerryWongBlog2 жыл бұрын
You can refer to the schematics here: www.kerrywong.com/2016/10/08/linear-mosfet-and-its-use-in-electronic-load/ (and there is a updated version: www.kerrywong.com/2017/01/15/a-400w-1kw-peak-100a-electronic-load-using-linear-mosfets/)
@jamest.50016 жыл бұрын
so it works like a potentiometer? until fully on?
@jamest.50016 жыл бұрын
I was wondering what the deal with the crazy priced FETs was!
@kostasb88836 жыл бұрын
Thank you!
@KerryWongBlog6 жыл бұрын
You are welcome!
@jamest.50016 жыл бұрын
does the larger packages dissipate heat better? are there and advantages of the larger packages?
@KerryWongBlog6 жыл бұрын
Yes, the thermal resistance is slightly less for the TO-264 devices compared to TO-247.
@papalevies7 жыл бұрын
I have had problems using electronic loads based on Mosfets for measuring low voltage sources. I have found that around 500mV Vds and below, the mosfet doesn't work.
@TheHuesSciTech7 жыл бұрын
A properly implemented MOSFET dummy load will be able to present a low resistance (close to the Rds(on) of the FET) all the way down to 0mV. Is your current-measuring resistor getting in the way? Burden voltage of multimeter being taken into account? Are you using a feedback loop with an op-amp that doesn't work with its inputs going all the way down to ground?
@crocellian29727 жыл бұрын
papalevies - Are you using a single supply rail to rail op amp?
@Telectronics7 жыл бұрын
Are there linear MOSFETs that are capable of few Amps at least 1A by 400VDC ? I would like to build an electronic load for mains applications. You know PFCs can go up to 400VDC and deliver 1-5A so there must be someway to load them down without resistors in kW range.
@KerryWongBlog7 жыл бұрын
IXTK60N50L2 seems to be able to handle 400V 1A (at least for a few seconds according to the datasheet), so you could use a couple of them. The maximum power dissipation is limited by packaging and 400W is about the limit any single MOSFET can handle.
@Telectronics7 жыл бұрын
Thank you for your answer it helps a lot! Oh you are right how could I forget the heat resistance of the MOSFET :) I have looked at fig.14 for the SOA and it seems it works reliable only at 300VDC for 1A. Did you refer to fig 13 or 14 ? It seems to me that, If I want to use it at 400VDC I should stay way under 75°C case temperature right ? If you compare fig. 13 and 14 you can see fig.13 says it´s ok to go for 400v where fig.14 says it will die then and the only difference is case temperature of the MOSFET. So I guess with 5-10 in parallel I should go for 400V 1A.
@KerryWongBlog7 жыл бұрын
Fig. 14 would be more realistic. If you look at the test data in the datasheet, this MOSFET is guaranteed to withstand 1.1A at 400V for at least 3 seconds. So with sufficient heatsinking, you should be able to reliably dissipate 200W or more for each MOSFET and you would only need 2 of these MOSFETs.
@Telectronics7 жыл бұрын
Yes you are right I see it. They cost 25USD at Digikey so yeah 2 are enough xD I test one at half power first...
@chikenpaww5 жыл бұрын
Just like bjt with more simple current unput
@rancid119999882 жыл бұрын
Great video Kerry. I have an electronic load schematic I was wondering if you would like to review? I emailed your youtube address with no response..
@KerryWongBlog2 жыл бұрын
Sorry, I receive a lot of emails. May not have time to attend to each one.
@rancid119999882 жыл бұрын
@@KerryWongBlog I understand, you are a very busy man. Should I send it to your email address?
@InssiAjaton7 жыл бұрын
Your massive heat sink is wasted and so are the fans. The cooling air should go through the rib area. You could gain some natural cooling, if the heat sink would be oriented so it allows a chimney effect. Better yet, the fans should add to the chimney effect!
@KerryWongBlog7 жыл бұрын
There are a few fans on the back side of the heatsink, I didn't bother turning them on as they are rather loud. The issue is that the heat resistance is not low enough and the MOSFET die was already very hot while the heatsink was barely warm since it is so big.
@TheHuesSciTech7 жыл бұрын
Given the size of the heatsink, and given the brevity of the test, the heatsink could have been wrapped in insulation and it still would have done its job fine through sheer thermal capacity alone.
@simontay48516 жыл бұрын
$18 EACH! F**k that. I ain't paying that much.
@KerryWongBlog6 жыл бұрын
Unfortunately, while these linear MOSFETs are good, they are really expensive. But for the same load you would need many more regular MOSFETs in parallel and would need more supporting circuitry so at the end it might even out.
@simontay48516 жыл бұрын
Would (IG)BJTs work better in this application as linear devices than FETs.
@KerryWongBlog6 жыл бұрын
IGBTs are typically used in higher voltage switching applications. While you could use IGBTs for electronic loads, they typically have a higher Vces and thus limit the minimum operating voltage.
@Pops1806 жыл бұрын
They are expensive because they are relatively new. Give it a year or so and they will be cheap. In the past, IGBTs were the product of choice for high voltage switching because high voltage MOSFETs were so expensive. Now most high voltage MOSFETs are a dime a dozen. I have abandoned IGBTs in my designs because they really aren't necessary anymore except for a few niche applications.
@steverobbins48726 жыл бұрын
Wrong, wrong, wrong! You should read a text book before you try to teach. For example, when a MOSFET is used in a "linear" application, like a voltage regulator, that does NOT mean the MOSFET is operated in the "linear" region of the I/V curve. Second, "saturation" is NOT when the MOSFET is "fully turned on". A bipolar transistor is "saturated" when it is fully turned on. A MOSFET is "enhanced" when it is fully turned on. A MOSFET in saturation means that it is "pinched off", so that the drain current is a function of gate-to-source voltage, and depends relatively little on drain-to-source voltage; this is what you showed when you sketched the ID vs VGS curve (but forgot to show the threshold voltage). It seems that you don't understand that the curve you drew applies only when the MOSFET is saturated. in other words, a saturated MOSFET acts like a voltage-controlled current source, not a voltage-controlled resistance. Also, a power MOSFET is not comprised of a bunch of separate little MOSFET chips inside the package; it is one silicon die that contains many MOSFET cells. I could write about 10 more pages about what you did wrong. Don't mislead people!
@KerryWongBlog6 жыл бұрын
Hi Steve, thanks for the constructive criticism, point taken. This primary goal of this video was to show the capability of the L2 MOSFET, there are lots of videos teaching the fundamentals of semiconductor devices. I certainly understand the fundamentals but the choice of words could've been better.
@chehar6 жыл бұрын
Yes, thank you for this correction
@thisnicklldo6 жыл бұрын
Yes, I stopped watching once it was clear that when he says 'linear region' he is talking about the saturation region, and vice versa. Nobody that confused about the simple stuff can be getting the hard stuff right.
@gluiangyang1156 жыл бұрын
Otherwise who you discriminate?native!!!
@felixcat43467 жыл бұрын
It would be nice if Kerry had not mixed up some semantic differences for clarity. I also think it is a bit confusing to try to promote a particular product and present it as tutorial on using mosfets at the same time getting people to buy one. It muddies the water.
@KerryWongBlog7 жыл бұрын
Hi Joseph, I am not affiliated with IXYs. Their MOSFETs are the only ones I could find with the power dissipation I need for linear operations. Of course you can choose any model you see fit.
@crocellian29727 жыл бұрын
Where exactly are these errors and this "promotion" you speak of? Really stupid comments.