#85: Basics of R2R Ladder DAC | Digital Analog Conversion, Tutorial R-2R DAC Thevenin Superposition

[@djtoddles8750]

I've never seen the "flip book" approach you used here, that's genius

[@friedmule5403]

Yes he do really deserve a big thanks because he do that! It is genius, simple and so illustrative that I hope everyone else would do the same! w2aew, thank you for doing that extra work and for sharing your knowledge with us!!

[@bunnythekid]

Every so often I come across a really great electronics video and I go to click subscribe - then I realise I already have. And it’s always you!

[@RaviShankar-db5jc]

Sir you are an incredible teacher....hands down

[@deanthomson8658]

you've got no idea the amount of stress this video just cured me of, thank you so much

[@cny02253]

You know, I learned all this stuff in college, but Alan -your K.I.S.S. approach, crystal clear presentations and concise treatment of these subjects are now streamlining my brain! (Which I really need in my advancing age.) Very much appreciated!

[@JeremyVeleber]

I really enjoy these videos. Your preparation and attention to detail, without becoming too technical, has allowed me to learn and understand at a level that I will likely use the stuff you are presenting. Thanks a whole bunch! Keep up the great work!

[@flanlemonjello]

I always enjoy your presentation style (and content!), but the analog PowerPoint animation is a whole other level of awesome! Thank you!

[@crocellian2972]

Really good. Thank you. I remember my undergrad p-chem lab exam had us doing the derivation of this. I flunked. Nice to see a master do it right. Please do more of this sort of thing. The Arduino kids are really learning almost nothing but silly cutesy junk. They can really benefit from people who meet them half way.

[@MrNBit]

I am learning electronics buy myself and your video has made allot of things make sense now. From how digital outputs work (constant voltage) to how transistors control voltage, and even how capacitors are used to clean up ac from a dc voltage signal. Great I can not thank you enough for your clean and detailed walk-though explanation! I have just purchased an old analog oscilloscope, cant wait to see pulses that can otherwise not be perceived :-)

[@w2aew]

Great! I'm glad my videos are helping you to learn electronics!

[@JanMoren]

Seriously good, informative video on a resistor ladder for digital to analog conversion. And yes, I do look at videos like this on a Saturday Morningside for fun :)

[@JanMoren]

I thought I posted this on g+, not KZbin. Now I can't edit it or delete it :(

[@richardsidler]

I got the post from you on G+, are they not one in the same now? Thank you I enjoyed the lecture very much.

[@JimGriffOne]

I remember learning a little about MIDI sequencing when I was younger, and I never quite got the concept of MSB and LSB until I learned about A/D and D/A resistor networks. Your video is by far one of the best on KZbin about explaining the concept of parallel D/A conversion. Thanks for making your videos. I should make some videos about own about my profession, but audio mixing and mastering really isn't one of those necessary things in life as electronics is.

[@SatyajitRoy2048]

You are the master of demonstrating complex things in the easiest manner. Even a small kid now can understand how R-2R DAC works. I am sure it would be less noisy than PWM DAC without all the switching noise?

[@rbmwiv]

Excellent video. Thanks for the great explanation of how everything works in a D/A resistor ladder converter. Very clear drawings and explanations. I learned this easily watching your video while the book I was reading was kind vague on what your video covered. Thanks again for showing me how it works. I will definitely be checking out your channel, from this video I can tell that you know exactly what why and how this stuff works and you are very good at explaining it in a very easy to comprehend way that the books don’t. Thanks again. I have said that too many times.

[@tradegrabber4854]

As always, awesome explanation with real life examples, thank you!

[@coreyk9518]

All electronics lessons should be presented through flip-books! Wonderfully lucid explanation of R2R DACs

[@REDACT3D]

great video bud. The gag with the pages flipping over, demonstrating the current flow through the r2r ladder, was a great visualization! didn't even need to get fancy with the graphics!

[@RazvanMihaiDudu]

Very educational, thank you. I love the way you pictured all the steps in the analysis of the circuit. Awesome!

[@Exo5432]

This helped me understand r-r2. I have resolved to watching this video as my electronics book didn't help me understand it much for my course. I shall share this with my fellow students.

[@w2aew]

I'm glad you found the video useful. Let me know if there are other topics that you and your fellow students have difficulty with, and maybe I'll do a future video on them.

[@Exo5432]

***** Wheatstone bridges :)

[@KominTater]

Very much appreciated, W2AEW! This and the rotating "TeK" video very nicely done, well paced lessons and the start of a much-needed refresher course, if I'm going to make any headway with some of the projects I've been wanting to try. The R-2R DAC stuck into an Arduino is a kick! I have all the parts but I doubt if I have all the patience. We'll see! Thank you for posting!

[@w2aew]

You can buy R-2R resistor networks from places like Digikey or Mouser - a lot less tedious to wire up!

[@KominTater]

Thank you, W2AEW, will def. look into the ready-made solution. But there are times when such tedium can be good for the soul. ;)

[@ibjavier]

Omg. Thanks a lot. I actually remember seeing your video a few months back. I think that is how I found your channel in the first place and that was when I subscribed. I will watch it again soon. Thanks again.

[@jimadams2473]

Nice!! An excellent tutorial on the R-2R ladder. I liked the way you illustrated the R-2R with the folding paper. Best explanation I have ever seen on this topic. Keep up the GREAT work. Nice lab, too. Thanks

[@CassetteMaster]

Fantastic presentation! I love the paper-flipping technique!

[@unklebidii]

I was not aware that I watched this...haha.. Right when I am looking into R2R ladders for an ADC0809 that I've been playing around with... Great job on the Thev and Superposition part..I have to go back and rewatch that as I note EVERYTHING. Thx Alan

[@andrewferg8737]

I feel like a caveman every time I watch your videos... Indistinguishable from magic.

[@andreaacme]

VERY USEFUL, one of the quickest self-made DAC converters I've ever seen :) I'm sure it will come in handy at a certain point. Thanks for sharing.

[@Neuroszima]

Only after i read "Art of Electronics" chapter 1 with voltage dividers and such i have now fully appreciated and went ahead of 3:10 for a magical "AHA!" in my head. What i mean is, i finally understood how does it become a "resistance = R". But that is not your fault, it is more of a personal obsession of mine. 4 months ago i had been jumping around many different topics and things i've watched were nowhere near close to each other (one time, what is oscilloscope, watching several GHz oscilloscopes and "WOW he can view gigabit ethernet, or transmission through wireless, does it really look like this??", another about what is a mixer, how to manufacture projects from Dave from EEVBlog... you get the point) but after i started reading this (very slowly btw, i should progress faster) book, everything seemed to finally click rather than being chaotic collection of facts.

[@JunkyardPhysics]

Simply brilliant. Thank you.

[@friedmule5403]

You are simply a fantastic teacher!! The part with the fold over paper make it so obvious and simple to understand! :-)

[@Mydrac]

I like a lot the video, especially the way you use the paper to explain, it is a system that helps to understand. Thank you.

[@neodonkey]

Brilliant. There is something really beautiful and elegant about the R-2R ladder.

[@Allan-mf1he]

Thanks understanding the weighting using a simple resistor network was easy enough. I struggled with the R 2R voltage mode model. This helps a bunch.

[@memadmax69]

I remember this stuff long ago and far away. Was working on z80's and such... this brings back plenty of memories thank you!

[@Fatkuh]

I love how you used the cut pages for the explanation! Great!

[@thecombatengineer7069]

binge watching all the circuit tutorials, trying to remember to like and comment on each as well

[@Auerc0re]

you should be teaching this .... i had to learn this 2 months ago and i didnt even understand a single word of what my teacher tried to tell me but now i understand it even though superposition could be realized with less resistors but more resistor values

[@w2aew]

Identical values are used to take advantage of the inherent matching in IC manufacturing.

[@christheother9088]

+Auerc0re He IS teaching this.

[@jj74qformerlyjailbreak3]

ScopeArt. My new favorite hobby. Thanks.

[@RAndrewNeal]

Your tutorial is on Tektronix's website in written form. That's pretty cool.

[@GuilhermeSampaioC]

You have great teaching skills! Thanks

[@electronicgarden3259]

Excellent! There's no other word for this.

[@krish2nasa]

Excellent explanation as always, Thanks for your time and efforts.

[@PA2OLD]

Hi, we used that network (with a bit of filtering) in the late 80s to get digital audio from a 8 bit PC Printer port.

[@BrianHensleyRULES]

You did it again Allen! Great video!

[@ibjavier]

Can you explain the PLL to me? I would like to understand the mathematics behind it but at the same time get a clear and basic understanding of it. In the meantime, I will look to see what other videos I find on youtube. Thanks.

[@Nermash]

Brilliant explanation of R2R DAC!

[@jstro-hobbytech]

You are an incredible teacher. A teacher whom I'd like to play paper rock scissors for that beautiful mdo of your's. Wow. I keep my eye out on ebay all the time. Instead of paying 3k last year for one and a k the year before (that I donated) I should've bought a second hand one. Haha

[@realtoy1]

Another excellent training video. Thank you!

[@Keep-Exploring128]

the art of DAC ... thanks for the great video

[@StephenMendes]

I made an R2R ladder video also ..... I show the staircase waveform on oscilloscope .... it's in my Electronics Projects playlist..... I subscribed..... great channel

[@haimt]

very good explained of R-2R ladder, thank you very much :-) genius.

[@GeorgeGraves]

Awesome video - thanks for showing the math for the R2R ladder.

[@TheRogerx3]

Useful and interesting... Who needs power point anyway. : ) Very creative on so-many levels.

[@ChrisGozzardThatPhysicsGuy]

Many thanks.. Got the PWM method working so I think I will try with the R2R method. :)

[@ydonl]

Ahrrrr, matey! :) I like this one. Gonna make one of these some day. I'm thinking about adding rotation in the analog domain... Hm! Multiply an analog value by a sine wave... Gilbert Cell, I think. Then... the full set: scaling. rotation, translation. Lots of multiplies; maybe multiplexed Gilberts so we don't need so many of them. Lots of oscillators, too. Fully over-engineered!

[@Deceneu6]

Big like for the explanation method!

[@DasIllu]

I remember vaguely seeing this in a german home computer magazine (64'er) in the early nineties. I always thought it's super convenient, but alas the userport on the C-128 even when driven by machine code was too slow to really have that level of fun with it.

[@gotbread2]

Very good explanation, also well done with the substitution!

[@TonyButchT]

All from YOUR desire to learn more! Thank You!

[@Aeduo]

That's how Disney Sound Source/Covox Speech Thing worked. A good few old games supported just that.

[@gamingSlasher]

Best explanation ever. Love it!

[@InsurgentX]

Fantastic video as usual. Thanks!

[@JanicekTrnecka]

I love this w2aew version of DaveCad :-)

[@ernieschatz3783]

AllanCad is much clearer.

[@robertjohnson4089]

great talk and i loved the demp

[@edmclaughlin4923]

Alan, did you have to adjust your X/Y coordinates when you switched from PWM to the R-R2 DAC and started writing PORTD and PORTB registers? I built a ladder very similar to yours and it seems to test out well on the "steps" test. (Just running up consecutive numbers and resetting to 0). When I tried applying my PWM coordinates, my initials where not recognizable although points and lines were and no flickering. Looked misconfigured. Same 2.7K resistors (2 in series for R2) and a 10nF to ground off the output. I am wondering if my sketch might be off but it seems pretty simple to do.

[@w2aew]

The only two things I had to do was to use the map() function to rescale the X values to 0-255 and the Y values to 0-64. Also, adjust the delay in the loop and/or the filter cap to ensure the points settle to make a clean, crisp trace.

[@edmclaughlin4923]

Been fooling around and yes, figured out you couldn't push a number like 98 into a six bit field. Went back to the Xmas tree and got that displaying nice. I divided all the coordinates by 5. I'll use the map() function for my initials and see what I get! Alan, I want to sincerely THANK YOU for all the time you take posting your videos. Thank you for uploading your knowledge and experience!

[@w2aew]

I'm constantly inspired by the nice comments and encouragement I receive from my viewers, so Thank You!

[@edmclaughlin4923]

***** Everything worked. Christmas Tree and initials are crisp and flicker free. Have to get a camera that is fast enough to show it!! LOL. Had to fool around with the cap filter and timings to get the right combo. Settled on a .1uF Mylar cap. I was only seeing points on the scope until I changed out the cap. Learned a lot about my scope in this project. Thanks again!

[@NanikT]

Just a dumb question ... does this R-2R Networks is exactly similarly to what we normally hear DAC ? if I understand it correctly. Sorry...still learning about electronics

[@electronicatutorial]

Doesn't the Arduino have analog outputs? I used basic stamp long ago. For hobby what do you recommend to be easier to program Arduino or Basic Stamp?

[@Shakespeare1612]

It seems that I can use this circuit to read four (or more) digital buttons, or switches. I would connect one side of the open switch to my high logic level, like 5 volts, or three volts and then the other side of each switch to b0, b1, b2, and b3, and then if the switch or button is connected (it registers a binary 1 on that line) and it will add an appropriate amount of voltage to the Vout. Am I understanding that right?

[@w2aew]

Yes, except that the output will be binary weighted for any single button push.

[@jamilfaultfinder]

Hi could you please tell me which mixed signal scope you use and its bandwidth thanks

[@yoramstein]

Great, thanks. Alan you got teaching talent. This paper equivalent cut outs which you add graduately are worth registerd as a teaching aid patent :-) great.

[@anthonymullen2599]

This video rally helped me understand r-2r network in a simple and uncomplicated way , thanks . Also i adoing my 3rd year project this year and there will bw ADC and DAC in it I am struggling to find material on speeds and settling times on DACs and wanted your opinion if possible Thanks

[@tsalgir]

thnks for your clear explanation. really love it

[@MsFireboy2]

Have you ever used the 74hc393 ic chip to build a 4 bit stair step generator before?

[@w2aew]

I haven't

[@MsFireboy2]

@@w2aew Ok. I’m working on one. Using in a Curve Tracer circuit.

[@zhangbotao0831]

a good teacher

[@Naviscoop]

great video, very informative, thanks a bunch :)

[@afterthought138]

really excellent video.

[@baldbadger7644]

I wish my high school teacher taught as good as one tenth of you

[@markderlo212]

flip book idea is great! but why did you solder 14 bit ladder if you used only bits b6...b0 for the presentation? all other buts are nit used so fir this example one port would do, right?

[@w2aew]

I built this for a project that used both a 6 bit and an 8 bit R2R for a scope XY display application.

[@markderlo212]

I got an impression that you built 14 bit dac, 8 bits on one port and extra 6 on another...

[@w2aew]

@@markderlo212 nah, it was 8 bits on one port to drive the X position of an XY display, and 6 bits on another port to drive the Y position.

[@markderlo212]

oh I see, how to find that xy dac clip ?

[@w2aew]

@@markderlo212 It's at the very tail end of this video

[@MsFireboy2]

Question Would a square wave input at 50% yield a stair step waveform?

[@ricktighe191]

Brilliant!

[@DAVET38]

Another good video. The combination of Thevenin AND Superimposition theory in one example is brilliant. Keep up the good work. You certainly inspire me to try new techniques and ideas. DAVET38

[@micomrkaic]

A great video. I have some beginner's questions. How do you select the magnitude of R? In principle it does not matter, but if it is too low it might load the digital source. Can it be too high? For example, very high resistance might add more thermal noise? Thanks in advance for any answers.

[@w2aew]

The resistor value is a compromise between the load placed on the digital source driving it, and the output impedance - and how it will be loaded by the circuit that "reads" the analog output.

[@odissey2]

I built R2R DAC using 0.1% 7.5k and 15k resistors. The expectation was to get 8-bit resolution with 8 digital inputs. Not so easy. Actual resolution appeared to be 7-bit, most likely due to variance in intrinsic resistance of digital pins of the microcontroller, estimated to be in 300-500 oHm range. So higher resistance (50-100k) might be beneficial. Yet another limitation was Vdd noise on digital pins, also limiting resolution to about 7-bits. Overall impression that 7-bit is a practical limit.

[@harisonk]

Just wondering, could you use this as a DDS circuit for some lower frequencies?

[@electronicatutorial]

Can you share the program I want to put my callsign on the scope too :-)

[@Observ45er]

I should add that with the right software algorithm, you can even do polyphonic music. (you're just adding binary numbers). 73, Steve

[@edmclaughlin4923]

You have an 8 bit and a 6bit ladder. You show us the 6 bit on your mixed domain. Is that your Y-axis and the 8 bit your X-axis?

[@w2aew]

Yes - I used 6-bit for Y axis because the screen is rectangular.

[@edmclaughlin4923]

Thanks, I get it. You are working with DWORD and BWORD in the Arduino. Great project.

[@Neuroszima]

Ok so real question is, can you go backwards and creat analog--to-digital converter?

[@MrNBit]

Thank you very much!

[@edtix]

End of the video made me laugh :D cool stuff!

[@fir3w4lk3r]

Great! Did you tested it as a DDS? :P :P :P

[@fredflickinger643]

Very cool🙂

[@arrshithrg5359]

is it possible to vary the peak to peak voltage coming out of the circuit

[@w2aew]

Being a DAC, the output is a function of the parallel digital word applied. If you need more resolution, add more stages. Max voltage is determined by the logic 1 voltage level of the digital circuits driving the inputs.

[@arrshithrg5359]

hmm so vmax can be digitally controlled , i just needed 60mv to 6 volts sine wave controlled digitally, is it possible ??

[@w2aew]

The output voltage can't exceed the logic 1 voltage level. So, you'll probably need to follow the DAC with an amplifier to get the voltage you need.

[@Crytek1337]

My analog audio output on my pc doesnt work, so im must use the digital one. Is it possible to use only one digital input? So, the resistors are voltage dividing the digital input so it can be read as analog? How can i get more bits if i only have one digital output? Hope you can answer me :)

[@w2aew]

The R2R DAC needs parallel digital input. If you only have a single bit source, then the only thing you might be able to do is to feed the data into a shift register. Although, you will still need and additional bit of two to click the data into the register, etc. the better thing would be to pick up a $10 Arduino...

[@Crytek1337]

Aha i see. Thank you for answering this quick, this is what i needen to know.

[@ZaKu573]

what Range of your oscilloscope of the amplitude output voltage

[@w2aew]

+ting yiu i'm not sure I understand your question. The scope was set to 1V per division, which shows the full 5V range of the R2R driven by the Arduino.

[@ZaKu573]

+w2aew do u have any social acc?i hv a few questions of assignment!

[@w2aew]

+ting yiu You can find me under the same user name (w2aew) on eevblog.com forum

[@ZaKu573]

+w2aew turn on resistance of 100 ohms & turn off resistance of 1G ohms, for each control a current up to 10mA, what the (R'ref) equal to?

[@w2aew]

+ting yiu I"m sorry, but this question doesn't make sense to me (out of context).

[@82abn34]

Thanks!

[@jstro-hobbytech]

Random fact. Modern high end tvs (oleds) will have to reach a refresh rate of 1k hz for them to achieve the smooth motion of those 'relic' crt displays our civilization ran away from. Imagine the processing power a pc would need to drive path traced graphics in real-time to achieve a perfect v-synch with that. 2000 dollar gpus have to use interpolation to create false frames to hit 4k60 now finally but cpus will take longer to evolve than the display tech because they can't match the parallelism of modern gpus to feed them fast enough. I rarely find a game the odd time I play one (as I get older) where my cpu can saturate the gpu with vertices fast enough to hit full utilization. Intel said they would be at 10ghz by now but they can't hit it with current 3nm euv silicon etching. The 3nm node itself is a feat of monumental human ingenuity and it's hard to believe only one company makes sub 28nm lithographic etching technology. Most ics these days have stayed at that node as it's more than sufficient for most smd ics. I believe all dip ics are on the same 140 something nanometer node for the last 15 or so years. It's why most Chinese ttl and cmos ics are somewhat reliable for most hobbyists to mess around with. I've stopped buying as much from them the deeper I go down this fun rabbit hole people like you make so infectiously approachable and fun. I've read more text books the last five years and taken more notes than I did in university learning about data mining algorithms back in the 90s haha. To be fair though there were not alot of books then so we read white papers and such. I graduated top of my class then went into policing ffs and now play catchup in my 40s hahaha. Best thing about early retirement has been learning about electronics and playing stringed instruments. I wish I was as good at electronics as I am at playing guitar. You should have a patreon, even if you don't need the money. I'm sure alot of us would show appreciation. If you give me your mso I'll donate 10k worth of test gear to a local non profit hahaha. (Admittedly though it wouldn't be fair as I'm half way there already) hahaha.

[@outlawstc]

I took a array of cd4066 bilateral switches and set them up where they could switch each R2R bit to either a common signal or gnd... pretty much made a R2R amplifier in that manner that could be digitally set by a micro port.

[@w2aew]

Sounds clever!

[@Tadesan]

Yeah, that's a cool idea!

[@Turjak_art]

nice thank you!

[@sc0or]

When r2r is feed with a current, the overall analysis looks much simpler. All you need is to divide the current by two at each stage. And a I/U stage is simpler and more precise than U stage. The only reason for a voltage ladder is a ghetto-dac, when fpga/soc is connected directly to the ladder.

[@Infinitesap]

Hi what about a video regarding ADC? Thanks for GREAT stuff :-)

[@w2aew]

Maybe someday...

[@Loundre3]

Try out making a SAR ADC, maybe someday. en.wikipedia.org/wiki/Successive_approximation_ADC

[@flurng]

Thank you, Alan, for another terrific, informative video! However, I'd like to stir things up , if I may, with a bit of debate: I submit to you, Sir, that this is technically not a digital-to-analog converter, but a binary-to-decimal converter, since it's output is still composed of discrete, non-arbitrary steps, rather than one smooth, continuous curve. Would you or anyone else care to refute my claim? ;^)

[@w2aew]

I wouldn't call it "binary-to-decimal", since the output is certainly not a decimal value. A more accurate description would be a binary to discrete analog or quantized analog. All DACs output discrete analog outputs. You can put a low pass filter at the output, whose corner frequency is below 1/2 the sample rate, that will "smooth out" the steps in the response. This is often called a "reconstruction" filter.

[@MrMac5150]

Your GOOD