It's RRI, past the rails even. Unless people do tricks, like choppers or GHz voltage converters on-chip, RRI circuits often have hefty offset shifts over the cm range. They transition between differential pairs, n-types to p-types, at some cm voltage.
CMRR doesn't affect my circuit... I just turn the pots until I get the triangle that I want.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
It's a start, not a finished product. Suggest a part; design or whine.
I'm up to 11 D-sized sheets of schematic on this board so far, and need a few more. My quota is a sheet per day, working around other stuff plus goofing off. The last, tedious stage will be to put in all the part values and reconcile all the signal names and off-pages and mux/relay driver pins and connectors and supply voltages and such.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
This refinement is fairly parts conservative- keeps you out of negative CM range of the comparator for -.75V lower triangle limit the upper limit is 0.3V lower than threshold so just adjust it higher...
Please view in a fixed-width font such as Courier.
. . . . . . . . . +5V . | . | . [100k] . | . | |\ . TRIANGLE >---[15k] --+----+----------+------|-\ . | | | + | >------ . | - | V -|+/ | . [10k] ^1N4148 | TH |/ | . | - | o . | | | P . --- --- | . | . | C . | o . | |\ | . ------|+\ | . - | >------ . V -| / . TH |/ . . . . + . 2.5 x V . / \ TH / \ . / \ / \ . / \ / \ . TRIANGLE / \ / \ . / \ / \ . / \ / \ . / \ / \ . / \ / \ . - . 2.5 x V . TH . . .
I can probably use +5, since it will probably only need to swing to
+3.5. But it still needs to swing negative, and the comparators are grounded, so it's prudent to limit comparator input current if the integrator swings to -5 for some reason. Two resistors are chyeap insurance.
That would work too. The MCP6567 will work to -0.3 volts input, times
2.5 should be just enough negative swing.-- John Larkin Highland Technology, Inc lunatic fringe electronics
Just about when I got my HP35, I also got a PDP-8 minicomputer, which cost about the same as four Chevy Impalas. But I couldn't use it on exams.
I did some fun stuff, like ship propulsion system simulations, on the PDP-8 with a teletype and 4K 12-bit words of core memory. Used FOCAL, a really neat interpreter.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
That's a nice idea, run everything from +-5, except that we don't stock any 4000-series flops.
I'd still need -5, no?
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Insults! Insults! It is not!
-- John Larkin Highland Technology, Inc lunatic fringe electronics
See my second post to your 9:51 post, add 0.3V bias to divider to keep out of negative CMR of comparators...
Blobby, I'm sure someone gave you everything you've gotten in your life. A lazy lefty like you couldn't earn enough to buy a No. 2 pencil. I had to pay my way.
Except with today's digital capabilities he could easily do this digitally with off the shelf devices. Or he could use a $200 piece of test gear. The only reason he is designing a circuit is because he wants to play.
-- Rick C
If you will please note, my reply was addressing the 555 triangle suggestion. Would you like to discuss that?
You did no such thing, you were born with a cheap plastic picnic spoon in your mouth..
I did already. In another post I pointed out that the capacitor could be charged by the same current source John is using, but you still have the problem of setting the voltage range.
The only reason John is not using a 555 is because he is being a bit of a snob and is playing. That is why in the post your just replied to I pointed out all the analog solutions are inferior to a simple digital solution. But John would have to hand that off to a coworker since he really doesn't do digital. Or better yet, he could use a piece of test gear... but that wouldn't be "playing".
-- Rick C
Nippling? I can imagine what the waveform looks like, but how does that arise from a fast rise-time?
I object to your tag of "snob". Electronics is fun stuff and you should be tolerant of those who do not take the path you think is most appropriate.
As I recall, JL is quite versed on TDR and picosecond stuff. Is that not digital?
Or better yet, he could use a piece of test
And I posted above "Electronics is fun stuff and you should be tolerant of those who do not take the path you think is most appropriate."
You are as free as John to take the path of your choice without condemnation.
And you were born with a dick in your mouth. You seem to have developed a taste for it.
You're the liar I've always said you were, Blobby.
Hey, the offset is up to 10mV anyway. Not precise!
--
Thanks,
- Win
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It takes an analog engineer to make it work. The usual description of that is "mixed signal" electronics, where your nice smooth analog signals get in terfered with by switching waveforms. Designing stuff around A/D and D/A co nverters is usually referred to as "mixed signal" design, but meeting the a nalog challenges of getting really fast clean switching edges is just as di fficult, and basically digital designers almost always come unstuck there.
A very skilled digital designer once expressed skepticism about a proposal I made to speed up something by realising it in ECL, with the observation t hat he'd seen that approach go wrong very often. I said that it had always worked for me, to which he responded "sure, but you are really an analog en gineer".
Plain/slow digital tends to be boring, so John, as the boss, tends to pass it on to the nearest junior engineer.
-- Bill Sloman, Sydeny
Krw calling somebody a "liar" lacks the force it would have if anybody else made the claim. "Liar" in krw-speak means "somebody who expresses an opinion with which krw disagrees" which roughly corresponds to "well-informed" in regular English.
-- Bill Sloman, Sydney
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