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Symmetric Amplification

In many amplifying topologies, the devices used(all that I know of) all have asymmetric voltage input characteristics. Are their any devices and/or topologies that give a true symmetric voltage input characteristic? For example, with matched devices a differential amplifier or push pull topologies can offer symmetric output even when the devices used are asymmetric. This is not the type of example I am looking for.

I'm more interested in a single monolithic device the has the inherent symmetric characteristics due to design/geometry rather than some paring up two asymmetric devices.

Tubes, bjts, mosfets, jfets, all have asymmetric characteristics. It seems that the asymmetry may be due to the asymmetric nature of electron flow? i.e., electrons only *freely* flow in the direction(or rather opposite) of the electric field and a tube exemplifies this. i.e. nature imposes this asymmetry and all designs will have to resort to "tricks" to overcome it.

Reply to
DonMack
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Class A amplifier? As a side benefit, you can fry your breakfast on it.

On a related note, I recently tried powering a front end with asymmetric supplies (+4V and -6V instead of +/-5V) to see if biasing the amplifier's input stage a little off the 0V rail would reduce crossover distortion. I tried this with two high spec JFET input op amps (ADA4817-1 and AD86something) with a gain of about 1 million in that stage. I could see no performance improvement. I concluded that modern op amps are so good that input stage distortion is negligible.

Nemo

Reply to
Nemo 

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Perhaps you meant "pairing up"?
Reply to
John Fields

Indeed... we are all twisted in our own personal way ;-) ...Jim Thompson

[On the Road, in New York] 
--
| 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     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Speak for yourself.. ;)

Jamie

Reply to
Jamie

The path travelled by light in a vacuum without gravity - i.e. 99% of what we call "space"

Reply to
David Eather

The edges of crystals come awfully close.

John

Reply to
John Larkin

Bob Newhart was pretty good at delivering them.

Reply to
krw

How about a still spider hanging on its strand of silk? The silk will be pretty darned straight.

John

Reply to
John Larkin 

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Since gravity is everywhere, 99% isn't 100%, and light _will_ be bent.
Reply to
John Fields 

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Awfully close isn't the same as being there, is it?
Reply to
John Fields 

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Got an example?
Reply to
John Fields 

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Not really.

Do you know why not?
Reply to
John Fields

Gravity is not everywhere - it is only where mass is. Hence light is straight unless to insist on measuring it near planets and stars (etc)

Reply to
David Eather

Get real. There are gravitational forces _everywhere_. So there are NO absolutely straight lines... except in Larkin-land... and that's because of the fairies ;-) ...Jim Thompson

[On the Road, in New York] 
--
| 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     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Symmetric in the local vicinity of an operating point is the best you can expect to find in semiconductor devices. There ARE some vacuum tubes that use beam-steering onto split anodes, and THOSE are as symmetric as the left and right halves of the fabricated elements.

Why ever would a symmetrized gain cell NOT be what you want?

Well, if you allow magnetic field as the input channel instead of 'voltage', a Hall sensor qualifies. It's not generally considered a useful amplifier, though.

Reply to
whit3rd

Incandescent vactrol.

John

Reply to
John Larkin

He *is* being real. Light travels in straight lines to an incredibly good approximation as soon as you are more than a few diameters away from a normal matter or plasma based gravitating object. If it didn't we would see the sky altering and being distorted around the moon.

Most of the universe is empty space so a ray leaving the any star will travel in a straight line by default unless it passes really quite close to or through a strong gravitational potential well.

The effect that Eddington measured at the total solar eclipse for stars with light passing extremely close to the sun was barely measurable at under 2" arc as predicted by Einstein against a reference plate taken six months later. The deviations from a straight line are tiny even for stellar mass objects at grazing incidence.

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So whilst you could argue that light doesn't travel in *perfectly* straight lines (to be accurate it travels along the null-geodesics or in classical terms along the path of minimal time) they are the closest we get to straight lines in the universe and span huge chunks of it.

The effects of objects in the way can be rather pretty through the influence of galactic clusters on even more distant objects.

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Regards, Martin Brown

Reply to
Martin Brown 

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Gravity doesn't exist between masses???
Reply to
John Fields 

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Rather cryptic.

You're using that as an example of what?
Reply to
John Fields

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