This is a fantastic video! I appreciate you giving several circuit examples, and also walking the viewer through each calculation/ equation. Incredibly helpful! Thanks!

really enjoyed this - no annoying excessive "showmanship" that can blight some youtube channels; factual and engaging with example circuits demonstrated. Great!!

The best video for LED driving. Thanks!

Realy nice vid with an "easy to understand" level of in-depth explaining of the function in the different circuits. The prectical testing and showing on the board with hooked up instruments was a charm to watch. Thank you.

Thank you for this! Learning a lot from your channel.

Best Video .... thank you Super film teoria + praktyka i wszystko jasno i przejrzyście

Excellent video Steve. thanks!!!

Brilliant, it helped me so much. So well explained, no fluff, only useful details. But if you want more visitors you need to dumb it down and spice it up.

Best Video on Led Driving.

Thank you! most instructive.

Great video. And I'm looking forward to the clock project and seeing more done with the GPS unit!

Thanks Steve.

Fantastic tutorial.

Very interesting. Thanks.

Excellent coverage...well done! I'd be interested to see how these techniques compare to using a JFET as a constant current source.

Excellent!

Very usefull. Thanks!

Great detail and info

Very good video. I'm looking for your upcoming projects. Very interesting.

Tip. If you want to roughly determine the forward voltage of unknown LED (no datasheet) without CC source you can assume lowest voltage - 2 V, put a resistor to drive it to about 5-10 mA, measure the LED forward voltage and use this voltage for your final calculations. The Vfw with 10 mA and 100mA will be pretty close, at least close enough for rough calculations of a resistor drive. Taking the datasheet forward voltage won't help you much because it'll vary from LED to LED and with temperature.

Great video, as all your vidos in your YT channel!!! :D do you plan to do some video on basic switching mode LED driver? Like somthing with or without specific IC?

This is excellent work. Thank You so much. I have a question, I am working on a project which involved about 12 LEDs in series and the current requirements are about 6A in stable position and about 12-15A at the starting point, which is way more than the current requirements in this video which is merely 250 mA. So, what do you suggest which Linear circuit i should be using ? Would the OP AMP circuit work for me if i adjust the Vref and Rsense to generate 6A of constant current or would it cause more than bearable heating effects ? Any help is really appreciated. Thank You.

Loved your article. It's a few years later now. There are COB leds on the market that are 100W and 200W. How could I drive those with a CC and be able to dim them? Maybe a topic for a new video?

Very nice. Any chance you could do a follow up video explaining the challenges of driving the opamp cc circuit directly through pwm? You hinted not going all the way down to off to get faster response times. Could you expand on that? Thanks!

great tutorial, I am currently using an LM317 on the base of a transistor with its emitter on a 1ohn resistor, this allows me to set a regulated voltage over the base and resistor (with a 1.2v drop using standard diodes so it can be set to 0mA) that I can easily adjust to set the current through the collector. I have even gone so far as to make it into a current source using an LM337 and PNP transistor. what are your thoughts on this type of regulator? I know vB-E is not constant but it does the job fairly well for what I do (slowly charging Li-ion cells from near 0v) I would appreciate your feedback thanks, will have a video of my inverted version up in a couple of days (before I was just using a 5v reg and voltage divider) ... wait this is the same as your dual transistor version is it not? what exactly does the small transistor do then? as the voltage at the collector stops the base current flow.

Hello Sir, Your videos are very helpful. I have a question, How can i make my boost converter which is a constant Voltage Source to Constant current Source boost converter?

Great video! Keep up the good work. I have a question about 7 Segment displays. On a Common Anode 7 Segment display the number of segments varies from 0 to 8 including the decimal point on each Anode (Digit). Based on my understanding of the unit I have each segment LED drops 2v and is up to 25mA. Therefore in a 4 digit display the load can vary from 0mA to 800mA. Also you are switching the load around 240 times a second minimum (240 / 4 digits = 60hz). It gets worst if you try and drive 8 digits. My question is.. Which way would you drive this setup to ensure each segment never receives more than say 20mA given that the Common Anodes would have to use a PNP BJT or Pchannel Mosfet on the high side?

Helpful, Please what is the maximum current OP-AMP linear Current Source can drive without dissipating much heat?

nice work! very informative. Can you make a possible future video covering frequency compensation for opamps? I like you opamp current source and i was doing something similar a few days ago using a NPN transistor. What i noticed was that if i plug in my Load to the current source, the load saw the full positive voltage rail for about 20us until current regulation kicked in. Is this normal and/or acceptable? If not what can u do to improve this?

In the last circuit, can I PWM the vref from the micro controller at 3khz frequency, will the circuit keep up with roll off set at 1.5khz?

Wondent linear regulators also be more economical when the LED draws so little current, that the quiescent current of a switching buck becomes a significant factor in the efficiency? I guess this is assuming that buck regulators have higher quiescent current than linear... I suppose in that case a really high value resistor would be best.

Hi Steve, thank you for your lucid explanation of the circuits. I have a question. When would it not be appropriate to use a opamp based current source to run 20 watt LEDs over a dc-dc constant current circuit with inductor

So you can PWM drive LM317? Any examples? I would like to drive LM338 using arduino to change led brightness and avoid having pot on 338 circuit. That is because the pot has to be wire wound else it dies, and these are expensive. Also digital control is way better.

Hi this is a very clear and great Video ! one question that I have is, For the example 2, if I have a series of LED that I want to use, lets say 3 LEDs, with your example 3.3 v, that means that the voltage that I need after the resistor is going to be 9.9 V ?

Can you possibly remember what were the Rgate, R, C, Rsense values you used. And what was the MOSFET and op-amp, and Vcc and Vref? I want to learn from this circuit and it would help my confidence if I started from something that works.

About the last schematic. I've had hard times stabilizing opamp current source. It's stable on the DMM, but when I probe with the scope it is quite noisy. Precision current source without stability is useless. I would like to see a video with using different opamps and different methods of smoothing the current. From "scullcom electronics" channel I got a response that I should use high slew rate (is that the same as high frequency opamp?). I haven't tried that yet. So you can add this somewhere in the list of video ideas.

Regarding 4th proposal: What exactly would be the requirements of such a driving op-amp? Especially when lower currents downto 200µA are desired? Have you got an go to IC? When simulating with the LM324 for example, I really only get garbage...

Hello, i bought recently 100 pcs of 3w led neutral white. And i am wondering how to make a driver (dimmable) but also a power supply for about 120W, about 40 leds. Thank you.

Which method is the most efficient dimmable led driver circuit?

I use the LM317 (NOT IN CONSTANT CURRENT MODE) to drive my LEDs and a computer fan together, the LEDs however have a joule thief in between the power supply and the LEDs and I'm doing that for a long time without any issues, that's why I don't get it why the LM317 is used in constant current mode to drive some LEDs... You'll lose the function of the variable voltage which is the reason that I built the variable voltage regulator with the LM317 in the first place and also the ability to drive multiple loads at the same time where one device needs a bit more voltage than the other so why would you change that to a constant current driver?