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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: 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.

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  • (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.

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    • (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.

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