[bombela]

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.

[Gordonjcp]

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

This is exactly the configuration described in the CD4069UBE datasheet, where single stages of the hex inverter are biased to the midpoint with a feedback resistor. This turns them into a surprisingly good programmable inverting amplifier, rather like an opamp without a non-inverting input.

[kayson]

The same thing would happen on silicon. It's just a question of transition time. I've seen power mosfet inverters on some board designs, but you're probably better off using a discrete logic inverter because it would be cheaper...

[Zondartul]

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)?

[bombela]

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.

[amelius]

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

[guenthert]

CD4007 comes to my mind, but that one is ancient (still available though in a breadboard friendly package).