Twin T circuit wanted

[snip] [snip]

Maybe Larkin is a graduate of the Al Gore School of Engineering ?:-)

[snip] [snip]

Larkin did send me some beer. But he hasn't helped me "privately".

I think Larkin has PMS. ...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

Admittedly I do get "panty-bunched" at arrogant ignorance. Larkin, you're pathetic.

[snip]

Show us the emitter current, Larkin.

What's the Q of the tank section?

Values you show, but with tank Q=100, it squeges. ...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

--
The wire resistance of L1 and the ESR of C1. 
Right click on the components and a little dialogue will pop up which
can be edited to modify the component attributes.

Hi Jon, I had a great time this weekend playing with magnetic equations and thinking about magnetization.. ala Feynman. (chaps

36+37, vol. 2) (If you read the chapters you might have found that he does things a bit differently than others. He defines the H field so that it has the same units as the B field. He also doesn=92t like mu- sub zero, but instead just writes it as 1/(epsilon=96sub zero times c- squared. =3D u0)) (I=92ll use u0 below because it=92s easier to write.)

Anyway for his system, If you make the approximation that the B and H fields in the magnetic material are linearly related then you can solve everything. (B=3DuH) With L1 being the gap length and L2 being the length in the magnetic material I found B to be given by,

B =3D u0*N*I*(1/(L1+L2/u)) So if L1 is much greater than L2/u, then the gap determines the field. (u is the permeability of the material) And you can also solve for the energy density in the material and in the gap. And from that calculate the inductance. For which I get, (A is the area of the material and gap)

L =3D u0 *A*N^2*I^2*(1/(L1+L2/u))

And the energy stored in the gap is proportional to L1 and that in the magnetic material to L2/u!

This is totally cool, I never knew! It=92s a relatively simple calculation; I wonder why no one had me do it in college? (=91Course they don=92t teach you anything about =91real=92 components in college.)

George H.

Say it seems like toriods are the perfect topology for inductors, do they make toriods with a built in air gaps? (It doesn't have to be air.)

--
I don't mind that sort of process at all, rather enjoyed it back when
I had employees.

However, I do work alone now, so I don't have the luxury of being able
to make stupid mistakes which will bite me in the ass downsteam
instead of being picked up in my shop at the moment, or soon after,
they're made.

Yes, you can buy physically severed and epoxied, gapped toroids, or you can have a formulation made or buy one that incorporates it into the medium itself homogeneously.

On Jun 12, 5:10=A0pm, John Larkin wrote:

I already posted class-C versions. Here's a class-A version using a "real" inductor, Q(L1) ~=3D 30.

R1-D1 keeps it linear, and prevents Q1 conducting in reverse mode and taking that "bite" out of the waveform's negative peaks. R1 also controls the propensity to squegg by preventing overshoot in the ALC/ AGC control loop.

Vcc =3D +5v --+--------------+------+-- | | | | | .-. | | | | e.s.r. =3D 1 ohm | | | | | | '-' | | | | | |_ || | | _)|| .-. --- L1a _)|| Rb | | C1 --- 1mH _)|| 47k | | 1uF | _)|| '-' | _)|| | | *| || | '---+--' || | R1 D1 | || | 220r schottky | || +--/\/\/----|>]----+ || | | || | .------------' || | |/ || +---| Q1 || | |>. 2n3904 || | | * || C2 --- +----------------. || 1uF --- | L1b _)|| | | 100nH _)|| | | | =3D=3D=3D | =3D=3D=3D | '--------------------> 5KHz output

Cheers, James Arthur

~~~~~~~~~~~ Version 4 SHEET 1 952 680 WIRE 0 -32 -112 -32 WIRE 256 -32 0 -32 WIRE 336 -32 256 -32 WIRE -112 0 -112 -32 WIRE 256 0 256 -32 WIRE 336 0 336 -32 WIRE 0 16 0 -32 WIRE 256 96 256 64 WIRE 336 96 336 80 WIRE 336 96 256 96 WIRE -112 112 -112 80 WIRE 0 144 0 96 WIRE 48 144 0 144 WIRE 160 144 128 144 WIRE 256 144 256 96 WIRE 256 144 224 144 WIRE 256 176 256 144 WIRE 0 224 0 144 WIRE 192 224 0 224 WIRE 0 304 0 224 WIRE 256 304 256 272 WIRE 336 304 256 304 WIRE 336 384 256 384 WIRE 0 416 0 368 WIRE 256 416 256 384 FLAG 256 416 0 FLAG 0 416 0 FLAG -112 112 0 SYMBOL ind2 320 -16 R0 WINDOW 0 81 50 Left 0 WINDOW 3 78 79 Left 0 SYMATTR InstName L1 SYMATTR Value 1mH SYMATTR Type ind SYMATTR SpiceLine Rser=3D1 SYMBOL ind2 320 400 M180 WINDOW 0 79 65 Left 0 WINDOW 3 74 34 Left 0 SYMATTR InstName L2 SYMATTR Value 100nH SYMATTR Type ind SYMBOL npn 192 176 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res -16 0 R0 SYMATTR InstName R1 SYMATTR Value 47k SYMBOL cap -16 304 R0 SYMATTR InstName C1 SYMATTR Value 1=B5F SYMBOL cap 240 0 R0 SYMATTR InstName C2 SYMATTR Value 1=B5F SYMBOL voltage -112 -16 R0 SYMATTR InstName V1 SYMATTR Value 5v SYMBOL schottky 160 160 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D1 SYMATTR Value BAT54 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 32 160 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R2 SYMATTR Value 220 TEXT 440 208 Left 0 !K1 L1 L2 1 TEXT 440 264 Left 0 !.tran 0 120mS 0 1uS startup TEXT -72 -56 Left 0 ;John Larkin's oscillator, adapted, from s.e.d. 8- Jun-2010 TEXT 440 152 Left 0 ;f(out) =3D 1/(2pi*sqrt(L1C2) ) LINE Normal 368 176 368 0 LINE Normal 384 384 384 208 LINE Normal 368 384 368 176 LINE Normal 384 0 384 208

Bigger C2 helps prevent squegging by keeping the loop more 1st order.

Moving L1b into the base is actually interesting. The c-b conduction then happens further above ground, keeping the emitter out of play.

John

Care to point out the mistake you're referring to? BCX70s are beta graded.

Maybe your models have problems, but they all seemed to jam about 5 mA into the led. I assure you that I can make this circuit light up a blue led.

But what's interesting is that you let your emotions cloud your engineering judgement, to the point of doing charge-pump simulations that obviously work and pretending that they don't work. That's very bad engineering, when your emotions blind you to reality.

I have figured out why you so dislike topologies that don't have working values. Does anyone else see it?

John

[snip LTspice Schematic]

James, How can you call it "class-A" when the emitter current is _not_linear_, _not_linear_, _not_linear_, _not_linear_ !!

All you've done is use a Schottky bypassing the C-B junction... otherwise it's identical.

I liken such oscillators to how you push your kid on a swing set. Giving a "nudge" every cycle.

To be "class-A" you'd need to sit upon the top bars and _continuously_ push and pull the ropes.

Class-A would require a linear amplifier with variable gain. ...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

Ah yes, I recently did that. Except, L = Phi/I (compare: C = Q/V), so you forgot to cancel the I somewhere. I wrote about it and more here:

Should be useful to lots of people who, like you, never got instruction in what the hell a real transformer or inductor is, or how to design one.

Well, mix 61 and 67 ferrites have low permeability. I'm not sure if that's due to fillers or magnetic properties. The B-H curve shows a rather wide hysteresis loop (about 7 Oe across), suggesting disturbingly high losses. I don't think powdered irons are even that high, though they lose energy through eddy current as much as hysteresis.

Powdered irons could be said to have built in air gaps, since they're usually made from a fine powder (like carbonyl iron, which is spheroidial), compacted and bonded with a resin. The metal density might be 70-90%, I suppose, which is a lot of airgap. Actually, I suppose density would have to be at least 97% for most types, as there are powdered irons with mu_r >=

75 (and I think I saw MPPs as high as 750, but those might be sintered, I'm not sure).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

^ 100ms

Nice.

Ed

y l

True, the emitter current isn't linear, but it is continuous and non- zero, so I call that "class-A."

That makes a big difference. It prevents Q1 saturating and from conducting b-c. And, without it Q1 conducts in reverse mode during negative peaks, making the i(c) not just discontinuous, but reversing in direction. That loads the tank, obviously.

That's exactly how I think of them too. A "nudge" each cycle (short conduction cycle) is what I did first. I call that "class-C."

Or you can pull continuously, harder at some times, not as hard at others. That gives the swing position a d.c. bias, but is otherwise the same, yes?

-- Cheers, James Arthur

the

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(A is

so you

Opps quite right. I set the total energy equal to 1/2L I^2 and forgot to take out the I^2 from both sides... Thanks,

George H.

ms/Elec_Magnetics.html

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"Obviously"? Q1 doesn't conduct in reverse with your values, but no Schottky... the current is always out of the emitter... though it does get awfully close to zero: -376uA and -12.5mA peak.

Class-A implies _linear_, does it not? Or do we have a Larkin definition for today ?:-) ...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

What a lark.

hm

Yeah, if Q1 sucks energy out of the tank, that loads the tank.

Huh. LTSpice says Q1 does conduct in reverse, a nasty little 5mA spike's worth. The schottky feedback prevents that by cutting the base bias enough to make sure the collector never gets that low.

I've always used "class-A" to mean the transistor conduction angle =3D

360=BA. Class-B means mostly conducting but sometimes 'off', and Class- C means 'mostly off.'

-- Cheers, James Arthur

JT has asserted that no transistor amplifier is ever class A, because all transistor amplifiers are somewhat nonlinear. That obviously applies to mosfets and jfets and tubes, too. Interesting theory.

John

What does "discussion group" mean? If I opine that Larkin's fiasco doesn't function as he claims, I'm labeled as a "cranky old git", rather than Larkin admitting he don't know shit. I suppose you want "warm and fuzzy"... no one disagree? ...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