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Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

researchgate.net

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Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#21

Post by bombela »

Zondartul wrote: post #11
bombela wrote: post #3

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 troubl…

Can you use non-complimentary MOSFETS if they have a dead zone (i.e. both are closed for some middle voltage, resultig in high-z output)?

Yes, I was alluding to it in my post. I did successfully build a MOSFET driver (to drive a big MOSFET for a DC-DC converter) using two tiny MOSFETs (tiny as in sot23 package) in push-pull configuration. I found two MOSFETs that did barely overlap. It seems to work well. And the power dissipation was very reasonable at 42kHz. Note that I am merely a hobbyist.

Using non well matched MOSFETs resulted in a rapid uncontrolled atomization of the MOSFETs.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#22

Post by mzs »

kayson wrote: post #12

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…

Which are clever?

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#23

Post by yababa_y »

kayson wrote: post #12

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…

The paper cites https://ieeexplore.ieee.org/abstract/document/8506644, which enumerates 582 possible topologies for two transistors, and 56280 for three. I imagine most are useless and/or dangerous.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#24

Post by MisterTea »

aidenn0 wrote: post #14
MisterTea wrote: post #6

Earlier quoted context omitted.

What stinks is that linear use has waned so much that most lateral mosfets are no longer produced. Everything is vertical switching for PWM control.

Wow, you aren't kidding. I just checked Onsemi and Vishay and neither makes lateral mosfets anymore. I'm surprised because many audio amplifiers still have a linear output stage, are those just always BJTs now?

Most of the linear amps these days are integrated devices that need a few supporting components and you feed a line level audio signal. Though you can still get decently sized BJT's and you can build your own amps.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#25

Post by kayson »

mzs wrote: post #22
kayson wrote: post #12

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…

Which are clever?

18 is cool. Folding is a really under-rated and under-utilized technique. Common-gate impedance matching is "standard", but 22 uses it to also generate differential current outputs which is cool - I imagine it sees more use in RF design. 23 is also interesting. 27 blew my mind. I'm not familiar with ultra low power techniques so that was cool to see.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#26

Post by drhodes »

foobarian wrote: post #7

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).

There is JADE (for education), which can be integrated into a blog or for teaching on the web. It supports hierarchical custom analog and digital modules, a convenient way to create test vectors, (docs for that are floating around) This tool was used by students to build and grade the BETA CPU.

https://computationstructures.org/exercises/sandboxes/jade.h...

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#27

Post by amelius »

kayson wrote: post #12

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…

> a few are genuinely clever

Another perspective is that it would take a computer only a few minutes to generate all these circuits and test them for usefulness in a simulator.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#28

Post by amelius »

bombela wrote: post #3

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 troubl…

You can buy push-pull configured transistor pairs in a package.

Re: Variations of Two-Transistor Circuits: A Tribute to the Versatility of MOSFETs

#29

Post by kayson »

amelius wrote: post #27
kayson wrote: post #12

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…

> a few are genuinely clever Another perspective is that it would take a computer only a few minutes to generate all these circuits and test them for usefulness in a simulator.

That's harder than you might think. How would you test for all possible uses? Even if you looked at something fundamental like an N-port, you'd still have to define metrics for usefulness and many of the topologies in the paper would evade most obvious circuit metrics.
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