I once made a single-transistor latch by accident. It acted as a single bit of memory and retained its value for weeks until I got bored with the project. I ha

I once made a single-transistor latch by accident. It acted as a single bit of memory and retained its value for weeks until I got bored with the project. I had been making magnetic snap-together circuits, so I had a bunch of small PCBs with simple 2- and 3-pin footprints and holes that I soldered neodymium disc magnets into. I put a big TO-220 N-fet on one of them, and stuck it to a laminated whiteboard so that the magnets stuck without shorting together, then I hooked it up to an LED as a simple high-side switch. When I bent the transistor so that its metal plane rested against the magnetic whiteboard, its gate would latch after briefly tapping either V+ or ground to the magnet which was connected to the pin. When the transistor's metal plane was perpendicular to the board, it didn't latch. Disconnecting and reconnecting the LED didn't perturb the 'saved' value, and neither did removing power overnight. And the same thing happened with a similar P-fet connected as a low-side switch. It probably wasn't a "real" latch; it was a very over-sized transistor with low gate capacitance, and I didn't try it with something like a 3904. I think it might have had something to do with the principles behind nonvolatile ferroelectric RAM, but I never did get to the bottom of it. https://en.wikipedia.org/wiki/Ferroelectric_RAM https://en.wikipedia.org/wiki/Ferroelectric_RAM