Re: FET Switching

[JohnRoberts]

Sounds like he needed a refresher on ohms law.... 100 ohms

I used to have a shop vacuum that turned out to be a little van de graf generator too. When I used to vacuum my office, it would charge me up so my hair would stand out.

I mounted a 2 meg resistor to a screw ground on the light switch. The arcs to a bare ground were too painful. Of course your buddy probably needed more than a few meg...

JR

 

[Dan Kennedy]

I've done lot's of things with the series/shunt switched 4066's as well as better defined DG-40x stuff.

I built my first big ol' mixer project that way back in about 1982, far as I know that beast is still in service.

The charge injection noise has never been an issue with any realistic impedance levels in the circuits. More noise has been caused by crosstalk related to logic/signal corruption.

But the step function click is always possible. For broadcast applications I've liked the SSM ramped dealies, I forget the number now, like 2402 or something...

 

[bcarso]

The drawback to most 4066-like gates is that momentarily the signal path gets tied to Vss. This is somehow the consequence of the tracking stuff that helps to keep the on resistance constant.

If you switch quickly enough and the Zs are low, it can be less of a problem.

EDIT: The 4016 parts (unless they are relabeled 4066, which sometimes manufacturers do because the nominal spec is met) do not suffer from this problem.

 

[PRR]

> oil-filled caps .... We left the shunts on for storage.

Plastic-film caps are obviously "electrets". Just not very good. Nothing to lock-in the charge. Except maybe 10 years exposed to high voltage and heat cycles.

Maybe pure Teflon cycled to 300F and back holds 90%, and polybalony hanging around the cap cage only holds 1%. "Negligible". Except that was 10,000V charge.....

Air-caps would seem to be too unstable in the dielectric to show electret effects. It just wanders away.

Seems like charge on oil would also diffuse, though slower. But oil has poor mechanical quality and they are usually paper caps flooded with oil.... maybe paper is an electret? Not that damp wad stuck in my printer jam-hole, but inside the cap the paper is 99.99% water-free.

One thing about a storage shunt: you don't ask "Was this cap drained?" I put no more trust in me than in co-workers. Start to pull a cap out, boss calls, by the time you get rid of him it's quittin time. Next morning, who remembers?

 

[Guest]

Back to switches;
did you consider BA3126?
Though, it is not FET...

 

[Guest]

LC4066 also...

 

[StephenGiles]

[quote author="PRR"]> oil-filled caps .... We left the shunts on for storage.

Plastic-film caps are obviously "electrets". Just not very good. Nothing to lock-in the charge. Except maybe 10 years exposed to high voltage and heat cycles.

Maybe pure Teflon cycled to 300F and back holds 90%, and polybalony hanging around the cap cage only holds 1%. "Negligible". Except that was 10,000V charge.....

Air-caps would seem to be too unstable in the dielectric to show electret effects. It just wanders away.

Seems like charge on oil would also diffuse, though slower. But oil has poor mechanical quality and they are usually paper caps flooded with oil.... maybe paper is an electret? Not that damp wad stuck in my printer jam-hole, but inside the cap the paper is 99.99% water-free.

One thing about a storage shunt: you don't ask "Was this cap drained?" I put no more trust in me than in co-workers. Start to pull a cap out, boss calls, by the time you get rid of him it's quittin time. Next morning, who remembers?[/quote]

What???