Capacitor Discharging with CMOS Gate

Bandpass filter and comparator, as noted elsewhere.

They are not idiots, they are not pathetic, and we've had lots of intelligent conversations and emails trying to figure this one out. I've applied 20 volts p-p from a 50 ohm generator and haven't managed to blow the chips. They've made lots of measurements.

Should I recommend you as a consultant? Could you make room from your busy schedule?

John

Do you have any spare ADC inputs on this system? Might be a good idea to quietly log the DC level at this input node, with time stamp. RC filter it so that big excursions still show. I remember a case where there was a totally unexplainable interruption every so many seconds. A SW routine caught that time interval. Everyone thought real hard and while gazing out a window there was a weak reflection way in the distance, every x seconds. Same repetition rate as the glitch (this is where you can really show off an aviator watch ...). Closed the metallic blinds, problem gone. Aha! It was some kind of military radar station on the next hilltop.

Sounds like radar from Moffett Field near San Jose.

Use to drive me nuts when I was at Philco-Ford, Santa Clara.

...Jim Thompson

Don't ignore those TV weather RADAR systems.

-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85.

Michael A. Terrell Central Florida

Oooooh yeah- almost guaranteed to blow the sig gen...

Yes, of course

There won't be any friggin consulting to it, have walked in many a situation to correct a multi-month 'mystery' in five minutes with people like that. Where are these people, WrightPat or Hanscom or someplace...too far if farther than five minutes away, especially for any defense related *crap*.

Yeah, not many sig gens can handle a load like this...

in (o)------------470r-----+-------+---------comp+ | | | gnd | | +---comp- L C | | | | | | gnd | | gnd gnd

Terrifying, just terrifying.

John

John Larkin wrote: > On Mon, 25 Feb 2008 08:15:16 -0500, Fred Bloggs > wrote: >

Is that 470R or 47R, either way, I know of at least one fairly popular lab grade type that would not like that at all...you should have used a constant impedance filter. See the tutorial in US6608536, know-it-all.

Cute. Patent what everyone already knows :-(

...Jim Thompson

Then ditch it and get a real signal generator :-)

I know, only been common knowledge 100 years, didn't bother reading past that he had the time constant equalities right...

The best damned RF generators anywhere are Rohde & Schwartz, it's the programmable video grade jobs that act up...

I take that back, any RF gen with reasonably precise ALC will not like JL's circuit, usually they just passively shut-down. The solution is very high tech, get that RL to -3dB or more usually does it, duh-huh, a coaxial attenuator...

Then get the rep who sold them to you out there and read him the riot act.

Hmm, I use lots of generators and my loads are typically rather weird. Transformers with all kinds of resonances and the like. I expect them to survive and not shut down. And they all complied (so far).

The only RS generator I have here is the old SMF RF generator. The most spectrally quiet gen I ever had. But the steel tube in the oscillator has become tired after roughly half a century and it's pretty much unobtanium :-(

Which tube is that ?

Don't know about that one, but I have an old Philco-Sierra generator that uses an ML7211X. They are pretty rare, anybody know of a source?

Barry

I'll have to open it up again, some German type (AF...?). Maybe I should rework it so a newer Svetlana or Sovtek tube fits.

If you do, open it up to find out, let me know.

Our convention is that 470r means four hundred and seventy ohms.

You know of a generator that blows up when it drives a 470 ohm load? Let me know, so I'll be sure to not buy one.

Oh, the reason to keep the input impedance high is so that one 10 MHz source can lock a lot of modules. The bandpass/comparator makes the thing pretty much indifferent about waveforms.

John

So they shut down when open-circuited, or when plugged into a high-Z scope input? I've never seen any generator do that.

Once they shut down, how do they ever recover?

John