8-Bit Adder built from 152 Transistors
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- เผยแพร่เมื่อ 16 พ.ค. 2024
- NOTE: The schematics incorrectly show the NPN transistors in reverse, with collector / emitter swapped.
This is my first attempt at doing a semi-serious project using digital logic. To really gain a good appreciation for the technology involved, i designed and built the circuit entirely out of discrete transistors instead of using pre-made IC's with logic gates (such as 74-series chips).
This adder is built entirely out of 2N3904 NPN transistors, 220k resistors for inputs, and 47k resistors for output pull-ups. There are a total of 152 transistors and 224 resistors, not including the LED resistors on the manual switch board. The first board in the stack uses an LM7805 and 10 uF capacitor to provide voltage regulation.
Because of the presence of a carry output bit on the 8th stage, this can technically output a 9 bit number. The A and B inputs are a single byte (8-bit value), so their maximum is 255, and the output can compute up to 510.
In the future I'm going to add a lot more features to this machine, like multiple RAM addresses than I can read/write to, a clock + ripple counter to increment the input bits automatically, and maybe even a binary-BCD converter which I could then use as an input to a 7-figure number display, which would give this computer a graphic output. I also want to add a reader for a 3d-printed punch card that will provide program instructions or data.
Music:
Kevin MacLeod - Groove Groove
Heatley Bros. - Dimension Drift
Prod Riddiman - Lost Time
Kevin MacLeod - George Street Shuffle
You've done a better job explaining the working principle of MOSFETs and BJTs in 3 minutes than both of my professors did in two semesters of semiconductor physics and semiconductor devices. Hope you keep making content
I was about to say THIS!!!
Because you're supposed to know the physics behind and should be able to calculate what is required. You're supposed to learn much more than any random guy watching a youtube video.
No, he didn't. He didn't explain the "working principle" at all, he presented a convenient mental model. He never said *why* BJTs act as current amplifier and MOSFETs act as voltage-controlled switches, only that they do.
I'm sure you'll remember the discussions of band gap, depletion regions, MOSCAPs, pinch-off, different types of dopants and their free electron/hole densities, etc. All of those concepts are 100% necessary for understanding *how* a transistor works physically. What was presented in this video is a shortcut which is good enough to understand a circuit diagram of a logic gate intuitively, but which is woefully inadequate for designing or verifying anything complicated.
Do you study computer science?
@@tissuepaper9962 Also: The logic described here is Wikipedia - "Resistor-transistor logic" and NOT Wikipedia - "Transistor-transistor logic".
Anyway, nice handiwork and presentation. And a reminder that we all make mistakes;) (What I mentioned above and the wrong emitter arrow direction at the NPN-Transistor symbols). Also: I knew, You knew something, which @braedenbutler4838 did not (or he forgot?). So he couldn't really judge that 3 minutes is a little tooooo less for learning and understanding the principles and physics behind semiconductors. Let's better take 3 years as a ballpark number. We aren't in a hurry, are we?:)))
In 1971 I was 15 years old and I've build a 6 bit adder using 84 transistors (all that I had) in NOR RTL gates. After a week, one of my coleagues built the same with NO transistors, using only two readio keyboards! He is now a mathematics professor at Penn State Univ.
thats awesome
In high school (1988) I designed my own (on paper) calculator using logic gates. Addition , Subtraction , Multiplication, Division. 8 bit multiplication was almost an A3 paper. Division is the most challenging one because you have floating point result. When I tried to design my own 8bit processor based on 8086 design I gave up because it was huge
Can you share the circuit. Let me try to bring your idea to life
@@shantilkhadatkar1195 This happened in 1989. Unfortunately I do no longer have the plans. But it is easy to make
I used Minecraft, when i added my first 2 bits. The feeling i cannot express
@@shantilkhadatkar1195 would recommend using several RISC-V sub processors to decode and execute the x86 instruction set. The program that runs on the sub processors is called microcode. That's pretty much alot of the way those HUGE processors work...
@@kayakMike1000 Thanks! Will surely look into that
As a an engineer i feel so privileged with the computing power we have today and also the amazing work needed to even think of making such machines in the first place.
Indeed back in the 90s. You had to wait like an hour to make a one minute 320x256 mpeg. Now people play games in 1080p and stream it live XD
I absolutely love this youtube channel! I came across this channel last year, and at the time I had a really good grasp on physical engineering. But at the same time I didn't no much of anything about circuitry, but after I came across this video I really got into working with electronics. Now only 1 year later I already know how to make a homemade cpu, and work with most basic circuits! Your videos really are inspiring. Now all I need is a video that motivates me to get into shape as much as your videos inspired me to learn circuitry! Seriously though thank you.
Great project! Its good for younger people to know that before the availability of integrated circuits, this is precisely how early computers that were made back in the late 1950 and early 1960s implemented CPUs and did arithmetic.
I'm part of that younger people
This is literally computer engineering fundamentals.
So true
Then tell this guy to make a video showing a vaccum tube computer
Awesome. I appreciate grit and patience to build this whole thing to an actual working device!
I've taken multiple electronics classes that explained transistors, and I think it this short video helped a lot more than the hours of lecture for understanding how they work.
Well done! I helped build something very like this 50 years ago at school here in the UK as part of a simple ALU. IIRC, the adder could be driven by a 50 khz mains signal and act as a clock of sorts. My recollections are hazy after all these years, but I do remember the device came from a magazine article which called it BEATLE, standing no doubt for something like Binary Electronic Arithmetical Tabulating Logic Engine or some such! Lots of soldering and great fun to put together!
This was very inspirational to watch even today - imagine how thrilling it must have been for the engineers who worked on the mainframes to see their designs come to life!
Vertical stacking of the boards was a great choice and looks awesome.
Awesome video! You really go above and beyond with your in-depth yet easy to understand explanations and animations, and one reason I haven't missed a video yet. I've messed around with digital circuits before, so I'm excited to see where you go. Keep it up!
This is a fantastic video, not to mention informative, I hope you follow on videos like these. Good job man.
This is absolutely one of the top explanations I have ever came across thank you
It is stuff like this that blows my mind!! It is so cool getting to see computers work at such a bareboned level. No compiler, operating system, or schedule of any kind. Just a man and his transistors.
Amazing project for any enthusiast. Huge respect.
I am reading "The Elements of Computing Systems" from Nisan and Schocken, and this was fabulous to watch as it is a more physical representation of what I'm learning. I wish there was a kit that I could buy where I can build this. Thank you for such a GREAT video. Much respect.
Education on multiple levels (transistors and logic gates) along with a practical demonstration that's a step up from a basic example to show why computers went from vacuum tubes to transistors. Sweet!
Mental amount of info packed into 12.5Min. Phenomenal.
This is excellent. Videos like these provides a solid understanding of building and knowing how today's complex CPUs and what computer engineering is all about.
Well produced video. The explanation and narration we're top-tier.
The kind of content we like :D
Fast and easy to understand explanation
Great approach to discussing this subject, and great performance of your demonstration.
Forgot to mention that this is a fantastic project and a fantastic video. Great work sir!
Gives you the appreciation of modern CPU's that cram millions if not billions of transistors in them! Very cool!
I read somewhere the division process is tricky as it doesn't really divide but add
Keep em coming!!!!
This explaination is more comperehensive than what I learned in college. This is a great resource!
Great explanations of physical logic. I've designed half- and full adders from 7400 parts (fits on one 10x10in board). Now I need to do at least a 4-bit transister adder with blinkenlights, of course! Thanks!
Excellent work, congrats on getting it working on the first try! Good theory and diagrams too.
Excellent video thanks. By the way, The NPN transistors has the schematic symbol of the PNP ones.
Bro can made GPU NVIDIA RTX 4090 28billion transistor just in home hhhh
Yes, but if you look at the pin names (BCE, ECB) you will see the difference
Straight to favorites ! You've assembled one of the best video explaining transistors in a very short and accurate manner that anyone interested can understand. Brilliant job, as long as this video is published, im going to show it to anyone who needs basic knowledge of these semiconductors !
So you didn't notice the blunder at 5:53 and later when he used the wrong type of transistors in the circuits: all the base-to-emmitter arrows are inverted. The arrowheads should be at the emmitter side in NPN transistors for the base-to-emitter current to proceed to ground voltage supply wire (the base-to-emitter positive current means that electrons, having negative charge, travel from emmitter to base, against the arrow--- but the arrows are all wrong in these circuit schematics). In PNP transistors, it's an emmitter-to-base current that is positive, as signaled by the arrow from emmitter to base.
The way you designed your circuits, the transistors on the schematic should be npn. However their symbol is pnp. Or am I missing something?
I think he got it mixed up
Yeah, i'm confused af
You're correct. I noticed the same thing.
PNP works the opposite way right?
@@yun-z pnp woks with the reversed current, if that's what you mean
I'm trying to learn electronics from 0 so this video helped me tremendously. I'll have to rewatch it a few times
Thanks!
I remember when I was going to school computers out side of labs was a dream and our professor had a big board with relays and switches that was a serial adder, ie. it added up all the bit sequentially. What a racket that made.
this was incredibly concise and well put together, i learned a lot! thanks!
Very useful vedio, it really helped a lot to figur out how computers work. I've been looking for such a video for a long time but I have never seen such a simple and informative video like yours. Thanks a lot.
Thank you for helping me on my journey to building a discreet scale 8086
Great project! I did something very similar years ago - I used the goldpins to connect the boards though, gave even cleaner look, also you can optimize the adder a little bit on the transistor level if you just try to do it directly in transistors rather than assembling it from logic gates.
Maybe the best explanation of transistor function, far better than of school books
Very good way to present and explain Electronics
There are discrete NMOS and PMOS transistors with built-in very robust ESD protection. They are very difficult to kill, because the gate is protected from ESD and overvoltage.
What a breakthrough compared to vacuum tubes. You've gained miniaturization and reliability. Transistors are the future !😊
Is this what modern day bait looks like?
I wanted to build a simple vacuum tube computer, but after watching this, realized the massive power needed as well as dealing with the heat of 100s of tubes. 1W/byte basically put this idea out of my reach
@@pauls5745 - I think that was 1 watt per tube, not byte. So for this circuit, that's 152 watts. The 200 volt power supply also poses another challenge (staying alive).
This is brought back memories of Electronics class in high school.
5:26 The thing to keep in mind about ESD is that the static charge being discharged doesn't have to directly conduct to the MOSFET element being ruin. Sudden ESD events typically involve such high currents (although brief) that the discharge induces too high voltages in MOSFET elements near by the discharge path.
Saved to my "applied science" library because it explains gate functions. Thank you.
Dude it's an amazing nostalgia for me to watch your video. It reminded me of the time I was studying this very topic 20 years ago. Thanks for the video and keep up the great work.
(P.S. now I teach Partial Diff. Eq. and other variations of PDE's to some eager young minds)
cheers
Very detailed and informed approach, kudos!
Anazing project, really admirable!
You actually can reduce the number of gates further if you use Pass Transistor Logic (PTL). With PTL, you can make a full adder with only 6 transistors. PTL is slower, but this shouldn't be a problem for what you are doing. Additionally, you will need to put a buffer stage (just two NMOSFET and two pull-up resistors forming two inverters should do fine) at the end of the PTL circuit, since PTL will result in a high impedance output. This will allow you to drive the LED. You should be able to make the circuit with at most 64 transistors using the design I specified, but it might be possible to go smaller than that.
For those who don't know I would like to add that the 8 Bit adder circuitry that he built in this video is also called a Ripple Carry Adder. There is another type of Adder that appears to look more complicated as additional logic is integrated into it. The more complex version of the Adder is called Carry Look Ahead.
Now for a simple 8 or even a 16 bit system a regular ripple adder would be more practical as it requires less components, is a little bit cheaper, easier to build, easier to debug and troubleshoot and takes up less space, and the evidence of propagation delay is nearly insignificant.
So why would anyone want to use a Look Ahead Carry Adder instead of a simple Ripple Carry Adder? This becomes more apparent when your word size (number of bits to represent a binary number) becomes larger, or the Scale of the Adder. Registers or buses with 32 bits could be implemented using either type but once you get into 64 and 128 bit word sizes... The issue then becomes the time delay for the carry bit to propagate across each adder within the chain of adders. This would slow down your calculations everytime you tried to add 2 binary numbers. So imagine a piece of source code that would go through a loop 100,000 or even 1,000,000 times and you had say an extra 100-200 nano seconds of delay waiting for the carry bit to propagate to the next adder in the series of adders. How much added time delay would there be within your computation of a simple iterative loop?
This would significantly increase the wait time for the computation to complete. Since transistors have become much smaller in size the ability to add more logic to a N-bit adder becomes feasible and practical to reduce this latency. What a Carry look ahead adder does is it predicts the carry and pushes it to the next adder in the series so that each of the consecutive bits within the word size doesn't have to wait to perform the calculation. In this situation the result is almost instantaneous. However, the larger the word size becomes the more the Look Ahead Carry Adder grows in complexity in an almost exponential fashion.
Some of the largest word sizes today can be as big as 128, 256 and 512 bits. However, you won't typically see these as your average or common bus size words. Most systems today are 64 bits as that is the bus size of the architect that propagates through the CPU's ALU. Yet these processors can have special registers that are 128, 256 and 512 bits in size which are required when performing multiplicative operations or vector intrinsic instructions.
Does that last bit apply to AVX512, Intel's XMX matrix multiply, and Nvidia matrix Tensor?
@@mitlanderson I'm not sure, I'd have to look into their implementation design, their logic diagrams and schematics to see what they are doing with them.
@@mitlanderson those would most likely be using logarithmic tree adders since the operands would be longer. Plus avx512 is infamous for its power consumption so most likely optimised for performance > minimum propagation delay
amazing video that takes us back to basics, thank you so mcuh
I just downloaded the video, dropped it into resolve and turned on voice isolation to get rid of the noise, it was driving me crazy. Apart from that, great Video!
As always awesome video man🔥🔥
Imagine having to build this with vacuum tubes, and their respective cooling systems, and putting them at a distance so they dont overheat... crazy how far tech has come
The first computer wasn't even electronic.
Very nice project, and well-explained. I would love to see something like this with a built-in bin-dec converter so you can input and output decimal.
Love this project, you inspired me to make my own, on pcb, I'm releived it worked first try!
Good to hear. I'm impressed you got it to work on the first try with so many components
Amazing sound quality
this is really cool! 😎 after reading forest mimms books as a kid, i always dreamt of making my own ALU and microcode processor out of TTL components - so it is vicariously that i watch your endeavours! thx for making this! ✨
i mean, you technically can build a microcontroller from transistors yourself but, its gonna take *a lot* of space
Thank you for your hard work. Also, thank you for teaching us a thing or two...
It would require me *at least* two hours to build one board, and probably another hour to find and fix any error.
I've assembled circuits just as an hobbyist, and not very often, but that made me realize how important is to understand well the theory behind a schematic before building one.
Everybody's gangsta until the board is flipped and compnents must be soldered in reverse!
I don't know why, but transistors put a smile on my face.
I designed a 16 bit ALU with parity predict in the mid 1970s for a large computer outfit. I was limited to about 5 or 6 levels of logic to meet the frequency requirements. All the gates were 3 or 4 input nands. Look-ahead carries were required to keep the proppgating delay low, especially in the partity predict logic.
Way back in the very early days of computing I worked for Control Data Corporation and this was how they did early addition using one small pc board as one logic element. Multiplication was done initially by simply adding the one number to itself the number of times specified by the multiplier. This used a lot of time and power and when early ICs came into use was replaced by using fast ROM memory which had all the answers in memory and was simply addressed by the multiplier and multiplicand.
I know how to build the entire ALU and CU with 256 bytes of memory and I still have the ability for parallel synchronization processing. The only thing I’m lacking is parts and time. Your video is extremely informative, especially with the type of transistor I intended to use for my design.
I really like the idea - possibly something I will build to show my students this autumn, but possibly in NMOS with the 2N7000.
Apart from the schematic error and the slightly wrong explanation of the p-channel MOSFET also a good introduction to RTL. By the way: modern CMOS chips have protection diodes on their input pins and are much less sensitive than the earlier versions which are still around in the literature.
Very cool! The bottom of the chain of “can I build it myself”. I was horrified after building Ben Eaters 8-bit computer and realizing replacing the EEPROMS and ram modules with logic gates would 10x the footprint of the computer
excellent explanations, good work.
The adder works in real time, without a clock. The sum updates as you enter values. We can see the carry propagation. First time I see this classic circuit in real life.
correct. one function of the clock is actually to slow the CPU logic down enough that the complex circuits like this have time to propagate and reach a stable (correct) value.
Wow.. 8 months later I came back watched this video became fascinated again.. Proceeded to write this comment to only realize you blew my mind already 8 months ago.
you are awesome my friend. how long have i been looking for this
Good work!
I learned something from this 😀 I never actually knew what ttl and cmos meant, never put it together in my head. I thought it had something to do with the operating voltage. looking forward to future videos. I've been struggling to build a redstone computer in minecraft for a decade. I get stuck on the control logic and other details.
Ah, wonderful. Just finished building a 14 transistor full after (time for 7 more, yipee) on a hand drawn+etched board (hell) and NOW I stumble across this.
Owesome! Very pedagogical, IMHO.
I have an original 7482 TTL half adder. 1971 is the date stamp. And it still works.
Great explanation!
This is inspirational. Thank you.
Looking at the 1 bit adder, I noticed that if you replace the two ANDs and the OR gate with NANDs, you get the same result saving 3 transistors per bit adder, for a total of 24 per full adder. Maybe it can be optimised even more.
Maybe he preferred something easier to assemble, aka faster
Elementary. You did a good overview!
This video was really useful indeed. I was just looking for how to create prototype CMOS gates out of discrete N and P E-MOSFETs, and I found the IC integrated schematics only everywhere, containing special MOSFETs with extra terminal for the Bulk. However, your "MOSFETs" are drawn here as JFETs. Weird, but they work as MOSFETs, so thanks for that!
Otherwise, your "TTL" circuits are neither the simplified TTL nor the RTL ones. They are somewhere between, but of course, I'm glad they worked perfectly for you. Also, you wrote accidentally PNP BJTs later. First it was OK, later they became PNP ones in your schematics, but you constantly mentioned "NPN", so that's fine. I guess.
Excellent videos. Thank you.
amzing tecnolagy good job brother
Amazing. Love the fact that you taught many people (including me) not only about transistors but logic gates too. Also I was wondering on how much volts dc you run everythingm
I'd guess 5 volts given that it's pretty common now (thanks USB) and because in his schematics you can catch glimpses of 5v.
Edit: He mentions using an LM7805 in the video description so it's 5v.
great video!! tjank for teaching me more!
A wonderful upgrade would be to add the 8 XOR Gates and the extra switch to convert it to an 8-bit Adder-Subtractor.
Great Video uwu.
It would be interesting to see someone build a complete computer like this.
that would take up a whole room, aka. the early computers
the crazier thing about those computers are made out of vacumn tubes
We used to make circuits like that in tech high school back in the 80's. Good times.
I love making logic circuits! I've already made a rudimentary neural network
Please make continuous series of this
Nice work!
Absolutely love it
I think that by now you already know that you did a great job explaining all the concepts of transistors and adders in this video, and I really think so, then I'll be focusing on something that you could improve, your audio quality, I heard a lot of noise in this video so keep the hint
thanks for the work
Wow great video! That must have been a lot of soldering
BEAUTIFUL
Very nice build man
Hooly crap I'm downloading this video, thanks for this!
Бесценный ролик! Я хоть и слабо знаю английский + в этой теме только начинающий, но все равно и принцип работы транзистора, и принцип работы логических элементов мне стал понятнее за счёт того, что все было показано наглядно; большое спасибо автору!
I remember the days of half adders as well. The military used individual units to build.
That development lead to the micro versions of today's technology.
And to think, in the early 50s, this would have been above top secret! Still, great explanation of basic fundamentals.
A valve computer would use less power if it used sub-miniature valves (Often operated at 28VDC). The TTL gates you're showing are actually RTL (Resistor Transistor Logic) gates.