Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs (opens in new tab)

Some of these are standard, a few are genuinely clever, but many are bad designs and I'd never let someone tape them out in production.

2. Connecting the body terminal to something other than the highest voltage is dangerous and we rarely do it except in switches and diff pairs. We'd never do something like this. You can't even connect the nmos body to the gate unless you're using "deep" nwells which is an expensive process step that most people seem to avoid these days

3. I hate it when foundries do this in their standard cell libraries. Its an extremely weak pulldown and I've seen problems in production caused by using this structure. You can make a much better structure with a third transistor and positive feedback where devices still aren't connected to the supplies, but you get a stronger pull.

4-6. These are current-mode logic, but you never see them made this way because they're slow and high power. Instead they're usually made with a tail current source on the "bottom" and resistors on top, which keeps all transistors in a faster operating region. They get used often in RF clock dividers.

16. Again, connecting the body is dangerous, especially when the potential is somewhat unknown, but this does get used in extremely low power/low voltage applications.

I didn't get through all of them, but it made me wonder - with two 4-terminal devices, how many possible configurations can you actually make?

If you happen to play with electronics, most circuits in the paper cannot be built at home realistically. Those circuits work best with MOSFETs built in silicon, with very precise tolerances.

For example the first circuit; the inverter; when Vin is low, the bottom NMOS is off, the top PMOS is on. And vice versa when Vin is at the high voltage suitable for the devices.

Statically this works pretty well. But the trouble appear during the transition of Vin between the two state.

Un the middle of the range both MOSFETs are likely conducting, effectively producing a dead short!

On silicon they will design both MOSFETs to control and reduce this effect as much as possible. If you attempt to reproduce this, you might be in for a magic smoke release moment.

I did manage to somewhat reproduce this without a constant meltdown with tiny discrete MOSFETs by using two tiny ones with the most complementary specifications as possible. The goal was to have them with the least amount of overlap in conduction with regard to their respective inputs.

What layperson-friendly tools are out there to simulate simple analog circuits? For years now I've been going to the ancient app at https://www.falstad.com/circuit/ but wondering that surely there must be something that Real Electronics Builders use. (I intentionally did not say Engineers because I assume that would be covered by the pricy and/or UI-challenged tools like spice and company).

I like how I've been able to use MOSFETs as switches for the past 5 years while being almost completley unaware of the other things it can do. To me, it's a component that uses a small (low-voltage, low-current, low-resistance) signal to switch on a much larger path. Anything that makes it not behave like that idea is just problems for me (I spent a better part of a day debugging a circuit that works fine with a 5V arduino but not a 3.3V ESP32. I don't think I've even built a circuit with two transistors (multistage amp, flipflops...)

I could have sworn I'd seen a reference to someone working out or cataloging all known-to-be-useful two-transistor circuits with bipolar transistors but I can't seem to find it now. Anyone know?

This is a fun reminder that a MOSFET is useful as a transistor, a diode, and a capacitor.

I'm getting a CAPTCHA page forever. Is there an open-access copy of this paper?