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linear ramp

The charge needed to pull up the open-collector driver has to come from somewhere, and it comes from the ramp current source, through the diode. So the nonlinearity remains. It will be more linear to use a hard driver and a super-low-capacitance schottky diode.

An open-drain gaasfet would work pretty well, but then you need the fet, and some gate driver parts.

The problem is that I need precision, namely every point on the ramp being in the same place every shot, and better than 1% linearity. That shoots down all sorts of simple circuits, and fixing them makes them complex.

John

Reply to
John Larkin
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Are we surprised ?, no. It's what is expected from kids in raging hormone mode and much, much worse. In fact, the women are far more creative in fantasy than the guys, as anyone who has worked in a production area staffed by women will attest. I worked for a transformer / hearing aid company in the late 60's, floor full of women on coil winding machines and felt lucky to get out of there intact on some days :-).

Long before the days of political correctness and other fascism that you get these days...

Regards,

Chris

Reply to
ChrisQ

That's not what he said about my wife. His several posts were more explicit.

He's a mean-spirited redneck who enjoys inflicting pain, by his own admission. He didn't inflict any pain on me, because I know he's a lying, grotesque asshole.

And he avoids all the interesting electronics threads. Well, sometimes he alludes to his superior circuits without posting any.

What's surprising what a creep this guy is, how he has no boundaries on being a jerk, that he will say *anything* to try to hurt people, and think he's winning somehow.

Sad, sick, repulsive, boring.

John

Reply to
John Larkin

Yep. I had a female-staffed production line at Dickson Electronics (thick film plus chips on alumina, 1970-1973). I used to regularly have coffee with the whole bunch of them and pat 'em on the butt when they went back to work. Now... I'd be jailed :-( ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

Ok, I was in lm339 mode and assuming a pullup resistor. 339 would not be fast enough and a comparator that is would be more expensive than the line receiver solution.

The ramp is the interesting part of the design and the area that I would want to experiment with a bit more, including the use of a small inductance. Ok, am pulling your tail a bit here, but gut feeling says part of the attraction for the current solution is: "wow, an op amp that is fast enough to bootstrap a 20nS ramp" :-)...

Regards,

Chris

Reply to
ChrisQ

I am not amused by anyone insulting anyone else.

My wife died in '07, so I presume this does not apply to me.

I would not call him an asshole even though I think his insulting comments are inappropriate and his attitude is that of a curmudgeon who is inflexible toward people of different political and religious persuasions. I can not read his mind, so I don't know if he thinks his insults are clever.

However, I like his posts where he suggests solutions to electronics problems just as I like your posts for fresh ideas (as in this thread). You both have capabilities way above mine and I hope I can continue to glean an education from you two. You both deserve respect.

Cheers, John

Reply to
John

I'm happy to play with ideas here, which is why I posted my circuit.

I did consider charging the cap through just a resistor and an inductor, but the numbers were horrendous. I also played with using a PNP transistor as the current source, which works, but needs temperature compensation or closed-loop control, which takes more parts.

The AD8014 is only a kinda-fast opamp, 400 MHz, about $2, probably good enough for this application. For a little more money I could have used an AD8009 or some such.

I do need a reasonably low output impedance to push the ramp into the next stage, where it gets used, so there has to be some sort of buffer. An opamp integrator might work somehow as the ramp and the buffer all in one, if the details could be worked out. It would need a good reset/release mechanism, nontrivial. And probably a fast voltage-mode opamp, which is not as common as fast current-mode amps.

One thing that's sometimes overlooked: at these kinds of speeds, transistor beta drops because of finite Ft. So discrete things that look appealing at lower speeds may not work as well.

John

Reply to
John Larkin

Hobbs

of

lot

almost

=20

That brought back an old memory of determining the Early effect "voltage" by finding the mean mutual intercept of the Ic vs Vce curves.

Reply to
josephkk

On a sunny day (Tue, 12 Apr 2011 15:26:50 -0700) it happened Jim Thompson wrote in :

You should be jailed anyways :-)

Reply to
Jan Panteltje

One interesting aspect of this 'discussion' was that, while watching "The Social Network" they made a couple of comments about BU and waitressing, and it made a little more sense! 8-)

Charlie

Reply to
Charlie E.

Larkin has no sense, let alone a sense of humor :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

g

Jim's "intolerance of ignorance" is in fact intolerance of people who don't share his blinkered right-wing world view. I first labelled him Jim-out-of-touch-with-reality-Thompson here on Jul 2, 2007 and I've not found any reason to change my opinion since then. Search on the phrase and you will find a lot of examples of Jim posting ignorant nonsense.

Of course I can fire up a 555 timer - I did it back in 1975 - as I've mentioned here - in the course of evaluating a bunch of timing circuits, and didn't much like the results. The only thing the 555 had going for it was the combination of the - tolerably - high current switch with the more or less adequate monostable, and since then I've always ended up going for better monstables and better switches in separate packages (when I've been forced to use a monostable).

Jim-out-of-touch-with-reality Thompson confirms his status yet again.

He doesn't like being shown up as a nitwit, and kill-files people who do it to avoid the experience. Note that this means that he doesn't get to learn which of the things he thinks he knows ain't so. He's intolerant of every form of ignorance except his own.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman 

--
I'm amused by the fact that you took the bait and are still fuming
about your wife being insulted, when what it's really about is that
you were trolled, well and truly hooked and, even after all this time,
don't know it. :-)

He really got your goat, didn't he?

Interestingly, he didn't insult her personally; he merely recanted a
tale about a certain group of women with a propensity to licentiously
display their "naughty bits" to voyeurs behind telescopes, and
inserted a little innuendo.

You did all the rest of it and, with your outcry of indignant rage, it
seems to me that: "The gentleman does protest too much."
Reply to
John Fields

What he did was show what an asshole he is. He admits that he will go to lengths to hurt people. Old age and senility are disinhibiting.

Wrong. Read his posts. He was very specific.

I think you're a senile asshole, too.

Blubber lover?

Yup, you're definitly an asshole, and a coarse, stupid one besides. Probably for the same reasons he is. I bet neither of you has learned or done anything new in decades.

John

Reply to
John Larkin

BU

True. I remember reading them.

He seems to be able to post them promptly on his website, with links, along with some other stuff. Oh that's right, you don't have a website.

I must admit that i do not care to watch people push each others buttons interminably.

Reply to
josephkk 

--
Oh, and _you_ don't, you hypocrite?
Reply to
John Fields

You remember poorly if you think it was "explicit". I keep a copy of all my posts. My first BU punch-post was _exactly_ one year ago today.

Stop feeding the Larkin troll and spare us all from his manic depressive behavior. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

Funny. A quick check of my website shows several recent patent issues... and there are more in the Patent Office queue... one of which is an extraordinary breakthrough... might make my name famous (instead of infamous ;-)

Marvelous, we've outed Larkin into his true asininity.

Now, let's move on and get Slowman out of our hair. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

[snip]

All 26 of my posts are now sorted into a BU_Larkin directory compilation. Not a single one ranks as "explicit".

What I recited above is absolutely correct. Plus Larkin has proved beyond a shadow of a doubt that he's an ignorant stupid... you fill in the blank... no entry, no matter how vile, can be wrong :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

[snip]
[snip]

Naaaah! Larkin isn't just a dick... he's a d*****ad :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

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