Multiplier

If you mean analog multipliers, that aren't used for RF mixing, then it's a dying breed and you should be asking about the "least likely to go obsolete next year".

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Analog multiplication isn't popular!

John

I mean among the analogue multiplier which configuration is commonly used?

Used in what context?

Gilbert cell or log-antilog. Occasionally duty-cycle, but that's not very popular any more, what with microprocessors being so cheap.

Why do you ask? Homework?

John

actually i want to write a history about the analogue and digital multipliers.

In that case you should be asking what _was_ popular. You should also decide if you want to extend your research back to vacuum tube circuits, or even mechanical multipliers.

IIRC (from being told, not from doing it), vacuum tube analog computers used x^2 circuits but provided no multiplication. If you wanted multiplication you observed that (x+y)^2 - (x-y)^2 = 4xy, and you went from there.

Going further back, there were a number of fire-control aids that were used in WW-II on both sides that used some exceedingly clever lever-and-cam arrangements to implement all sorts of 2-input, 1-output functions, including multiplication.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

You know, if I had money to burn, I'd bet you a nickel that I could patent this technique. :-)

Look at:

James Long, Ph.D., P.E. Analog and RF Consulting Engineer History of Mixer Technology (And Other Stories of Misplaced Credit) Things are seldom as they seem. Skimmed milk masquerades as cream.

Quote: "... All of mixer technology in use today was mathematically known several hundred years ago and reduced to practice by 1935 when the DPDT vibrator modulator was used in low frequency amplifiers. By 1949 this function was performed by the 7360 vacuum tube in radio circuits and six vacuum tubes in rocket telemetry circuits. ... [ Scroll further to get ] Mixer Basics ..."

Oh, then you'd be interested in the old and obscure stuff.

Motorized 10-turn pots, with servo drive, used in old analog computers.

Duty-cycle modulation, as mentioned.

Bulk-effect (carborundum?) nonlinear resistors, Beckman maybe.

Matched photoresistors.

Tube or transistor bias modulation, as used in AGC circuits.

Software!

There's also hybrid analog-digital modulation, like chopping an analog signal with a PWM or Delta-sigma or digital rate multiplier signal. I've seen that used in semi-analog flowmeters. In Moscow, to be exact.

A couple of the MIT RadLab books have analog computational circuits, and semi-electrical mechanical multipliers and integrators, like for torpedo aiming and navigational applications.

There's lots of stuff around about digital multipliers. The analog stuff is more obscure.

There was a weird beam-deflection vacuum tube that sort of multiplied. It was mostly used for SSB generation. Anybody recall the number?

John

Glenn mentioned it in the post parallel to yours: the 7360. AFAIK it didn't 'sort of' multiply -- it _did_ do two-quadrant multiplication straight up. You had a regular old grid that controlled the total amount of electrons in a beam, a pair of plates to collect electrons, and a pair of deflector plates (as in a CRT) that deflected the beam to spray more or less onto one collector plate or another.

I've never used equipment that used them. Someone once mentioned to me that they were real 'nerdy cool' equipment, but tended to be sensitive to magnetic fields (which would steer the beam when you didn't want them to).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Early analog computers (e.g. the EAI 231R) used vacuum tube quarter square multipliers, available at the patch panel as X*Y.

The later machines (Simstar) had the same topology but used monolithic multipliers (AD534) to perform the squaring function instead of diode function generators.

Kevin Gallimore

The ones I used had servo multipliers.

Am 30.12.2010 21:12, schrieb Tim Wescott:

I still have a working ham radio transceiver that uses the 7360 in the balanced modulator of the SSB generator(Yaesu/Sommerkamp FT401/505). Would have preferred it in the second receiver mixer. Even bought some RCA spare tubes when they were EOLed.

Gerhard, dk4xp

You're an old fat! I haven't seen that type of modulator circuit, in years.

Jamie.

A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station.

The 7360.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

And the linearity is quite excellent in the active range. You can even stack three of them and make a true four-quadrant "Gilbert" cell.

Like all tubes, cutoff isn't very elegant, so you can't overdrive it and get like >40dB unbalance at the same linearity. But they're usually used as balanced mixers, so that isn't an issue.

There are also multiple-control-grid tubes like 6HZ6 and 6BE6. The dual-control pentodes were used for FM demod and mixing. The heptodes of course were used in every AM radio in existence. These work because the cathode and first grid make a virtual cathode with respect to the second grid, getting single quadrant multiplication.

It's like a JFET variable resistor, except you get as many grids as you want which reduce crosstalk to nil. There is no single semiconductor component which has anywhere near the same performance characteristics.

Speaking of FM demod, there was also a "sheet" pentode which used a modulated beam's space charge to excite a tuned control electrode, thus detecting the frequency shift same as a ratio detector. These were understandably sensitive to magnetic fields.

There was also an FM modulation tube, the phasitron, which harnessed magnetic fields to generate FM, actually PM, but the modulation coil did the FM-to-PM conversion thanks to its phase shift.

Just about anything you can think of doing in solid state, you can create a single vacuum tube that does it. Modulation methods, memory storage, analog to digital conversion, image conversion, you name it. Only problem is the damn things are hard to make with photolithography, so we end up using millions of costless transistors to do the same things.

I wonder what it would take to build a vacuum-state convolutional error correcting decoder and MPEG decoder. And hey, it could be the CRT itself, too -- the movie companies would love it, no wires to pirate the signal from!

Tim

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

I made it to the National Science Fair with the project "The Cathode-Ray Tube as an Active Circuit Element." Didn't win anything, but it was fun. I met and pal'd around with Amory Lovins, the kooky environmentalist.

He had hair then.

John

Gates used the 7360 for the video modulator in their VHF TV transmitters. I had both a 90 W and a 500 W on Ch 8, and the modulator deck from a 5 KW model, while in the military. It was a lot like dimbulb, always wanting attention.

--
For the last time:  I am not a mad scientist, I'm just a very ticked off
scientist!!!