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posted by chromas on Thursday April 19 2018, @05:43AM   Printer-friendly
from the one-is-all-you-need dept.

Submitted via IRC for TheMightyBuzzard

A flip-flop is one of the most basic digital electronic circuits. It can most easily be built from just two transistors, although they can and have been built out of vacuum tubes, NAND and NOR gates, and Minecraft redstone. Conventional wisdom says you can't build a flip-flop with just one transistor, but here we are. [roelh] has built a flip-flop circuit using only one transistor and some bizarre logic that's been slowly developing over on hackaday.io.

[...] The single-transistor flip-flop works just like any other flip-flop — there are set and reset pulses, and a feedback loop to keep the whatever state the output is in alive. The key difference here is the addition of a clock signal. This clock, along with a few capacitors and a pair of diodes, give this single transistor the ability to store a single bit of information, just like any other flip-flop.

That's damned nifty.

Source: https://hackaday.com/2018/04/18/the-one-transistor-flip-flop/


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  • (Score: 2) by c0lo on Thursday April 19 2018, @05:47AM (16 children)

    by c0lo (156) Subscriber Badge on Thursday April 19 2018, @05:47AM (#668883) Journal

    The output is a square wave for 1, and nothing for 0.
    Maybe it worth building a quasi-quantum computer with it?

    --
    https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
    • (Score: 0) by Anonymous Coward on Thursday April 19 2018, @06:03AM (9 children)

      by Anonymous Coward on Thursday April 19 2018, @06:03AM (#668889)

      Use more capacitors.

      • (Score: 2) by c0lo on Thursday April 19 2018, @06:18AM (7 children)

        by c0lo (156) Subscriber Badge on Thursday April 19 2018, @06:18AM (#668892) Journal

        Lose more time in delays. With the transistors so cheap, why use capacitors when you can etch transistors?

        --
        https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
        • (Score: 1, Touché) by Anonymous Coward on Thursday April 19 2018, @07:46AM (1 child)

          by Anonymous Coward on Thursday April 19 2018, @07:46AM (#668920)

          Because hackaday wants to use a single transistor rather than flip-flops.

          • (Score: 2) by c0lo on Thursday April 19 2018, @10:37AM

            by c0lo (156) Subscriber Badge on Thursday April 19 2018, @10:37AM (#668984) Journal

            Because hackaday wants to use a single transistor rather than flip-flops.

            Don't get me wrong, I do appreciate it, as a clever hack, that is. It may be useful someday.

            --
            https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
        • (Score: 2) by bob_super on Thursday April 19 2018, @07:48AM (4 children)

          by bob_super (1357) on Thursday April 19 2018, @07:48AM (#668922)

          Because you want many billion on one piece of Si, so anyone who opens the door to using less transistors is welcome.
          The next guy might refine this design and give us a significant step in memory density.
          Or it could be a dead end.
          But it's worth exploring, just in case.

          • (Score: 4, Insightful) by c0lo on Thursday April 19 2018, @10:23AM (1 child)

            by c0lo (156) Subscriber Badge on Thursday April 19 2018, @10:23AM (#668977) Journal

            Because you want many billion on one piece of Si, so anyone who opens the door to using less transistors is welcome.

            It's a single transistor and two diodes. Guess what two diodes are equivalent with?

            --
            https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
            • (Score: 2) by RS3 on Thursday April 19 2018, @05:04PM

              by RS3 (6367) on Thursday April 19 2018, @05:04PM (#669162)

              I'm not an IC designer, but I recall that most diodes in ICs are just 1/2 of a transistor. I forget the reasoning but basically it ends up being easier in the process.

              While I'm at it, I'm not so thrilled with this circuit, but to be fair I've been doing circuits for a long time. A standard flip-flop is 2 transistors and 4 resistors. This thing is 6 resistors (one for the input is not shown!), 2 diodes, 2 capacitors, 1 transistor, and no partridge in a pear tree. And _must_ be clocked, even if you aren't doing clocked logic.

              Capacitors are always a pain in an IC, and can only be very low capacitance value, on the order of a few pF. This thing would be huge on an IC scale.

              There are 4-layer semiconductors which will remain in conduction once triggered on, and can be triggered off. They're not used much in logic because they're slow.

              http://www.circuitstoday.com/scs-silicon-controlled-switch [circuitstoday.com]

              https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/silicon-controlled-switch-scs/ [allaboutcircuits.com]

              http://www.circuitstoday.com/gcs-gate-controlled-switch [circuitstoday.com]

          • (Score: 2) by The Mighty Buzzard on Thursday April 19 2018, @11:12AM

            by The Mighty Buzzard (18) Subscriber Badge <themightybuzzard@proton.me> on Thursday April 19 2018, @11:12AM (#669004) Homepage Journal

            Oh it's a dead end. It's a neat dead end though.

            --
            My rights don't end where your fear begins.
          • (Score: 0) by Anonymous Coward on Thursday April 19 2018, @08:48PM

            by Anonymous Coward on Thursday April 19 2018, @08:48PM (#669291)

            why use capacitors when you can etch transistors?

            Because you want many billion on one piece of Si

            How will we make connections for many billions of corresponding external capacitors, when copper pillar pitch is dozens of μm?
            Or shall we include these lolhuge capacitors on-die, just to make it bigger and more expensive than using more tiny transistors?

            He uses two 1500pF caps for clocks down to 200kHz. Scaling that to a minimum clock of 1GHz, that's "only" 0.3pF.
            I did a little research to double-check my intuition on this; I found data relating the 65nm process node first, so that's what I went with.
            At 2 fF/μm2, which is optimistic, each capacitor is 12μm by 12μm. Considering a 6T SRAM cell being well below 1μm2, that's easily enough for dozens of flip-flops.

            I won't say it can't have some useful application somewhere, but cramming billions of flipflops in a chip definitely isn't it.

      • (Score: 2) by DannyB on Friday April 20 2018, @04:42PM

        by DannyB (5839) Subscriber Badge on Friday April 20 2018, @04:42PM (#669701) Journal

        Use more capacitors.

        Eat more capacitors.

        sign placard worn by a cow

        --
        People today are educated enough to repeat what they are taught but not to question what they are taught.
    • (Score: 1) by tftp on Thursday April 19 2018, @06:05AM (4 children)

      by tftp (806) on Thursday April 19 2018, @06:05AM (#668890) Homepage
      As the comments to the article say, it's not a flip-flop, but a single-bit DRAM cell.
      • (Score: 2) by c0lo on Thursday April 19 2018, @06:19AM (2 children)

        by c0lo (156) Subscriber Badge on Thursday April 19 2018, @06:19AM (#668893) Journal

        A bit that takes a while to read.

        --
        https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
        • (Score: 2) by kazzie on Thursday April 19 2018, @09:49AM (1 child)

          by kazzie (5309) Subscriber Badge on Thursday April 19 2018, @09:49AM (#668961)

          Sure, but that's no excuse for not reading TFA!

          • (Score: 2) by c0lo on Thursday April 19 2018, @10:20AM

            by c0lo (156) Subscriber Badge on Thursday April 19 2018, @10:20AM (#668975) Journal

            I read it. It's intellectually interesting, I can't find a use for it myself for the moment, good to keep a bookmark on it.

            --
            https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
      • (Score: 0) by Anonymous Coward on Thursday April 19 2018, @07:02AM

        by Anonymous Coward on Thursday April 19 2018, @07:02AM (#668910)

        When I see "flip-flop", I think "bistable multivibrator".
        That typically has 1 connection each for power, ground, input, and output.
        It's sometimes used as a divide-by-2 element (e.g. to get octaves in electronic organs).

        FTFS: a clock signal

        What this thing is is a D flip-flop ("D" for "data").
        As you say, that's a 1-bit RAM.

        -- OriginalOwner_ [soylentnews.org]

    • (Score: 1) by GDX on Thursday April 19 2018, @08:51PM

      by GDX (1950) on Thursday April 19 2018, @08:51PM (#669296)

      If you go to the io page: https://hackaday.io/project/112126-one-transistor-flipflop [hackaday.io] there is an improved version: https://hackaday.io/project/112126-one-transistor-flipflop/log/135957-improved-version [hackaday.io] , that have a output of constant +v for 1 or and 0v for 0.

  • (Score: 5, Informative) by ese002 on Thursday April 19 2018, @06:33AM (3 children)

    by ese002 (5306) on Thursday April 19 2018, @06:33AM (#668900)

    I get the challenge of designing a flop with only one transistor as a defined goal. It's clever. It's fun. However, practical chip level design is concerned with total area. This design uses three diodes. Three diodes is at least as big as two bipolar transistors. So, you are up to three transistors of area before evening considering the seven resistors and two capacitors. Those aren't free either. I suppose if you could imagine transporting this design back to the pre-IC age, it might have some use. Caps are resistors are relatively cheap at board level. I'm sceptical that three diodes would be cheaper than two transistors and the complexity of the access protocol is a concern. The revised design does improve that though, at least on the output side.

    • (Score: 2) by frojack on Thursday April 19 2018, @08:41AM (1 child)

      by frojack (1554) on Thursday April 19 2018, @08:41AM (#668936) Journal

      My thoughts exactly, but also you forgot the clock.
      Sure, you might have a clock anyway hanging around on a board but adding it to flip a single bit of storage seems a bit of desperation. The second transistor would be all around cheaper and more reliable.

      --
      No, you are mistaken. I've always had this sig.
      • (Score: 2) by kazzie on Thursday April 19 2018, @09:45AM

        by kazzie (5309) Subscriber Badge on Thursday April 19 2018, @09:45AM (#668959)

        You could argue that there's greater benefit when you need multiple flip-flops (all driven by a single clock), but the designer states (in the project discussion) that that's most likely to be useful if you're building your system out of vacuum tubes rather than modern transistors.

    • (Score: 2) by The Mighty Buzzard on Thursday April 19 2018, @11:14AM

      by The Mighty Buzzard (18) Subscriber Badge <themightybuzzard@proton.me> on Thursday April 19 2018, @11:14AM (#669005) Homepage Journal

      Yup. It's not going to revolutionize anything but it's sure enough a neat hack.

      --
      My rights don't end where your fear begins.
  • (Score: 3, Funny) by DannyB on Thursday April 19 2018, @02:40PM (1 child)

    by DannyB (5839) Subscriber Badge on Thursday April 19 2018, @02:40PM (#669115) Journal

    Flip Flops can be built from a single electromechanical relay.

    When you're up, you're up.
    When you're down, you're down.
    When you're only halfway up
    [_] You're neither up nor down
    [_] You need a different pull up resistor
    [x] Your flip-flop is broken
    [_] You're using base 3
    [_] Is a superposition of two states
    [_] You haven't had enough to drink
    [_] Viagra or Cialis
    [_] Is a topic of ongoing study and research not yet sufficiently explored

    When you're neither up nor down is when your winnings equal the amount you've spent betting so far.

    --
    People today are educated enough to repeat what they are taught but not to question what they are taught.
    • (Score: 2) by BsAtHome on Thursday April 19 2018, @04:34PM

      by BsAtHome (889) on Thursday April 19 2018, @04:34PM (#669154)

      Ehm, why so restrictive? I think all choices are applicable.

  • (Score: 1, Troll) by Knowledge Troll on Thursday April 19 2018, @05:26PM

    by Knowledge Troll (5948) on Thursday April 19 2018, @05:26PM (#669171) Homepage Journal

    So if I have exactly one transistor I can make a flip-flop? No, I need 1 transistor, 1 diode, 1 cap, and 1 clock signal.

    So if I have exactly two transistors can I make a flip-flop? Yes, yes I can, with only two transistors.

    How many components does it take to make a 1 transistor flip-flop? At least 4.

    How many components does it take to make a 2 transistor flip-flop? 2.

    Is that a single transistor flip-flop? No

    This is clever but very poorly named and takes itself way too seriously.

    I hate hackaday.

  • (Score: 0) by Anonymous Coward on Saturday April 21 2018, @07:29AM

    by Anonymous Coward on Saturday April 21 2018, @07:29AM (#669998)

    with a few capacitors and a pair of diodes,

    How many of these do you need per flip-flop? Because a pair of diodes is already 1 transistor. And capacitors take up even more space.

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