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Re: Twin T circuit wanted

My first real job was a research assistant in microwave spectroscopy, a summer tech job. Two grad students on the same project spent the entire summer hunched over a Friden calculator in a small room, calculating rotational resonances for some organic thing. My PC could do all that now in, probably, a millisecond.

It is just about the only portable schematic format the industry has ever seen. Not a bad editor, but the circuits seem to wander all over the screen as you zoom. I have to keep selecting my whole circuit and dragging it back into sight.

John

Reply to
John Larkin
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[snip]
[snip diverting tactic and subterfuge]

You're wrong John. And I've got your ass this time :-)

Unfortunately Win doesn't understand how the oscillator works either. Disappointing :-( ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

What would determine the sinewave amplitude?

John

Reply to
John Larkin

Yep. "Ooopses" happen. As soon as I describe it on Sunday or Monday, you'll see how simple it is to understand.

Off to SFO at dawn... NO I'm not seeing Larkin... I'm heading to Palo Alto ;-) ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

I passed it to you, not to "rag" on you, but to have a "father figure" show Larkin the error of his ways.

But you didn't do it :-( ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

Larkinese: "There's no point in arguing definitions. The circuit does what it does. I used AGC to mean that there's an amplitude detector that compares the output swing against a reference and feeds back on a circuit parameter (transistor transconductance in this case) to servo the amplitude to a target."

Larkin can keep jockeying, trying to find a way to weasel into "correct". However, the paragraph above, direct quote from Larkin is WRONG.

The circuit does indeed oscillate, and control amplitude... but not as Larkin opines. It definitely doesn't function as he claims.

Isn't there some young buck out there who can analyze circuits ?:-( ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

I don't appreciate being thought of as a father figure.

But so far as the circuit goes, I've thought about it a bit and feel comfortable with my understanding, so far.*

It'd be nice if you'd state your point, rather than making endless disparaging remarks. Do you like thinking about signal-current pathways, rather than voltage gains, OK, great, I like that too, spell it out. We'll take a look.

Have you considered that while you may have a specific concept in mind, there may be other ways to adequately express the same phenomenon?

  • Not having yet put a pen to paper, a keyboard to spice, a component to analysis and measurement, a soldering iron to a breadboard, or presented a probe to a scope. :-)
--
 Thanks,
    - Win
Reply to
Winfield Hill

Late at night, by candle light, John Fields penned this immortal opus:

I'm speaking to Jim, not his side-kick.

Could be "The Three Jays" too.

-YD.

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Reply to
YD

Late at night, by candle light, Jim Thompson penned this immortal opus:

EXCELLENT!!! I can bad-mouth the silly old bastard to my heart's content and he'll never be the wiser.

Instead of a kill list I use a watch list, for grabbing the bodies of posts by people who usually are on topic. I had to take JT off it due to his political spamming and general negative attitudes.

-YD.

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Reply to
YD

Hi Jon, I hope you=92re not offended if I say that the first time I read this I thought it sounded crazy.

I took vol. 2 of =93The Feynman Lectures of Physics=94 down to the creek when I got home this evening. In chapter 36 he does ferromagnetism. (do you have a copy?) He does an electro-magnet near the end. (36-5). Early in the chapter he says that if you are willing to accept the fiction of magnetic monopoles, you can think of ferromagnetism as the magnetic analog of the polarization of dielectrics.

And so I totally accept your picture=85 though I understand it differently. Thanks!

Oh Feynman says the energy loss is the area enclosed by the B/H curve.

George H.

Reply to
George Herold

Bad choice of words, I guess ;-)

When I was in my forties I had sweet-young-thing (female) employees who said I was a father figure to them :-(

I only meant that, since Larkin side-steps me like the plague, and calls me "cranky ol' git", I thought he'd listen to you.

Hint before I run out of town for a few days: replacement energy.

I _will_ write it up upon return. It's really quite simple... at least fundamentally... you can get crazy performance by pushing the turns ratio.

Hint #2: What does transconductance have to do with a large swing oscillator? ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

Maybe, but your pc doesn't drink beer or chase cute college girls. ;-)

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Reply to
Michael A. Terrell

ime

Or

ts

s

ng

That's cool, so at a year and 1/2 I'm not that far behind. (Well I've only been doing circuit design for ten years...Still way behind)

George H.

Reply to
George Herold

A lot depends on how fragile your ego is. If you are determined to always be "right" in public, or you are determined that someone else is always wrong, you'll be a fathead and not learn anything.

Of course, there are some people who are AlwaysWrong.

John

Reply to
John Larkin

There was an explanation of the operation of a similar type of oscillator in Electronics World (formerly Wireless World) by Ian Hickman in the July issue. It is also in the book "Hickman's Analog and RF circuits). The circuit analyzed there is a Hartley oscillator with the feedback into the base but that is only a minor difference as one can be changed to the other by redefining where ground is.

As the oscillation amplitude increases the cb junction becomes forward biased and that does a couple of things; not only does it divert base current but through reverse transistor action causes the resonant circuit to be clamped, dissipating energy. Also it reduces the conduction angle where energy is added to the resonant circuit by splitting the current into two pulses - a balance then results when the energy added each cycle is equal to the energy lost.

kevin

Reply to
kevin93

:-) ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

Describing yourself, John ?:-) ...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     |
             
      The only thing bipartisan in this country is hypocrisy
Reply to
Jim Thompson

John gazes into the mirror (guffaw) and details for us his... err... our dilemma.

Yeah... sure... bub.

Reply to
BlindBaby

1 volt. That might be a bit hot, as I noted in the post. I did that on purpose, thinking a smaller conduction angle would give better frequency stability. You know, let the L-C ring unmolested as much as possible? Might not be helpful though--if the drive is sine-ish, the tendency to pull might not apply. Not sure.

Yes, class-C.

I like the schottky. Takes trr(b-c) out of the equation.

James

Reply to
dagmargoodboat

I prefer smaller drive, a tenth or so p-p on the emitter. Maybe even less, basically class A.

The whole thing behaves differently if the secondary drive is large and the transistor conduction angle is small: the emitter voltage will swing down, way below ground, and pull the base down with it before the collector voltage gets down to ground... blasting a spike of collector current into the tank. Then it will swing way up and turn the base off. Brutality! Chaos!

I prefer a more delicate touch: the collector dips down elegantly, like a swan landing on a pond. It just barely touches the water, err, emitter, and together they remove a bit of charge from the base cap. And then it flies away. Did I mention the sunset in the background?

John

Reply to
John Larkin

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