Using zener diode to protect test circuit?

Interesting result is that the 74HC04 isn't as good as the simple

...Jim Thompson

For this test you'd have to trust your spice FET models near 0V, which as we've discussed is in the subthreshold zone, where most models are notoriously faulty. 'U04 parts are popular for linear amplification, etc, where the spice modeling issue also comes up. One step in evaluating a model is to measure the transfer function of some real n- and p-channel parts, which either Paul or I will do for some ON Semi low-voltage unbuffered MiniGate inverters in the next few days. It's a continuation of what I started with the 2n7000 and some other JFETs and power mosfets.

I modeled this with X-FAB CMOS (integrated circuit) models which DO model sub-threshold.

I know that they work... I'm in a hearing aid project where virtually everything is operated sub-threshold. And also VERY noisy :-(

I'm using PSpice Level=7 / HSpice Level=49, none of this Level=3 s*it for me... they only do modeling that crufty for discretes.

...Jim Thompson

See...

Newsgroups: alt.binaries.schematics.electronic Subject: Active bridge rectifier using cmos hex inverters (from S.E.D)

- WinsRectifierHCU04.pdf Message-ID:

I forgot that, in May 1997, I had redesigned ON-Semi's unbuffered inverter (...U04) to fit their change to Chartered Semiconductor's foundry.

...Jim Thompson

This is good, and I envy you your model, but it should still somehow be verified as correct for the parts we're able to buy.

What version of NAV are you using?

If it was really there it got there from something in your machine or news server.

I run the latest version of NAV, and am a paid subscriber to the automatic (almost daily) updates.

I just scanned the original here and it shows no problems.

I also scanned a downloaded copy to see if a virus was somehow inserted.... neeeeerp!

I also run SpyBot, ScanSpyware and AdAware at least once a week; plus I have a hardware firewall, so I think I have a clean machine ;-)

...Jim Thompson

John, I just realized that you referenced a text message. Where's the virus ?:-)

...Jim Thompson

Naaah! You'd still have BVCEOrev back thru from the load

...Jim Thompson

That's very nice, can you show us the spice-model code?

Sure. It's been 8 years, so it's out of NDA...

Subject: Re: Active bridge rectifier using cmos hex inverters (from S.E.D) - WinsRectifierHCU04.pdf - CharterModels.zip Message-ID: References:

...Jim Thompson

I read in sci.electronics.design that Jim Thompson wrote (in ) about 'Using zener diode to protect test circuit?', on Sun, 24 Apr 2005:

Are there any NPNs with a higher VEB(BR)? Aren't PNPs better for this characteristic? A PNP in the 0V is worth an NPN in the +V, surely?

Maybe put a diode in the base lead to gain an extra 0.7 volts of protection. Since it's a 5V input, that might just be enough to make it perfectly safe.

Stepan

I read in sci.electronics.design that Jim Thompson wrote (in ) about 'Active bridge rectifier using cmos hex inverters, was Using zener diode to protect test circuit?', on Sun, 24 Apr 2005:

WARNING!!!! Norton AV found W32.Beagle.AG@mm virus in this message and has removed it. Virus scanning of outgoing messages is in force here.

I read in sci.electronics.design that Jim Thompson wrote (in ) about 'Active bridge rectifier using cmos hex inverters, was Using zener diode to protect test circuit?', on Sun, 24 Apr 2005:

That's rather what I suspected. It's not on my machine. But I thought it best to send a warning, just in case.

I read in sci.electronics.design that Jim Thompson wrote (in ) about 'Active bridge rectifier using cmos hex inverters, was Using zener diode to protect test circuit?', on Sun, 24 Apr 2005:

I couldn't see it as an attachment or anything, but then I don't know whether a virus can now (e.g. as of today!) hide itself in some way. I wasn't motivated to try too many experiments before I let Norton kill it.

Would a few hundred nanofarads worth of decoupling caps in the load matter though? I know that certain things like LEDs can be damaged by very low reverse currents due to localized heating in the die, due to non-uniform reverse breakdown over the entire junction, but is that the case for transistor be junction?

stepan

I should have mentioned that there aught not be much charge left on the decoupling caps by the time you disconnect and re-connect the circuit. So I wonder how much abuse an EB junction can take. Yes, I don't think anyone would want to see an electrolytic in there.

Stepan

You OUGHT to know the answer to that... zeners aren't worth the powder to blow 'em to hell when they're under 5V.

...Jim Thompson

See Aubrey, Jonathan understands.

So much for the value of a PhD ;-)

...Jim Thompson