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Are hybrid parameters useful for design?

look at the datasheet? They're on bunches of others, mostly older, too.

Not in my world. Feasibility is almost always controlled by how much of each I can have at the same time, so the geometric mean would be much less useful than knowing where the cliffs are.

Nobody has actually admitted to using h-parameters for actual design that I've heard of. I haven't, have you?

And the h_FE argument of John S.'s is ridiculous, because it's a large signal parameter, i.e. I_C/I_B, whereas h parameters are small signal, i.e. h_fe = dI_C/dI_B (or i_C/i_B, as it's usually written, but that's exactly the same thing).

And h parameters don't actually simplify anything, anyway. They were originally touted as a way to get round the measurement problems of y and z parameters, namely oscillation on the one hand and RC rolloff on the other.

But all they are is a way of organizing a whole two (2) linearized, frequency independent approximate equations for a transistor circuit that is far better described by hybrid-pi. The labour saving is trivial, far less than the effort required to calculate the stupid things in the first place.

Honestly, folks, is h_re really more useful than VAF? VAF and C_CB are actually a decent first cut at predicting low frequency reverse-transfer behaviour over a wide range of conditions, which h_re isn't.

H-parameters are textbook curiosities.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs
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Hey, you're wrong by a bit lower than 1.5% (at room temp, which of course I don't remind what it is :-)

Another useful value is 1K = 4nV/rtHz

or that 3 uA of photocurrent has a 1-Hz

--
Thanks, 
Fred.
Reply to
Fred Bartoli
[snip]

So are PhD's ;-)

Seriously, VAF is just a parameter in another STYLE of modeling. And math is math is math. "Textbook curiosities" tweak the mind to think of alternate solutions to untenable problems. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Sure thing. But it's a reasonable approximation over a wide range, because it's physics-based. h_re depends linearly on collector current, for a start.

And at least I'm not in a _pathology_ texbook. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

h-parameters can be complex math expressions, not just fixed numbers. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Sure again. But then where's the benefit? A 2x2 matrix written out with all sorts of algebra and stuff sort of defeats the point of the exercise--it's far clearer just to write it out the usual way.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

Phil wrote a great book on electro-optical design, with a goodly bit of low-noise electronics included.

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He also serves as our reference LPTM (Large Physicist Test Mass).

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

The 'benefit' is the ability to easily model things that don't yet have models. Let the simulator cope with the Algebra. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

On Mon, 15 Oct 2012 12:16:19 -0400, Phil Hobbs wrote: A 2x2 matrix written out

If it is a text-book curiosity why bother to write it at all! Of course, Jim says he very occasionally uses it - which means he rarely uses it. Indeed, why should he? Oh, God! We got our time wasted on this!

Guys, now we are really discussing issues! Thanks!

Reply to
rajibbandopadhyay

I am so sorry, I was writing when JT was writing too. But do we require these simplified models at all?

Reply to
rajibbandopadhyay

I'm talking about the benefit of the H parameter format, i.e. organizing two (2) equations into a matrix. All it is, basically, is a way of collecting terms in an equation.

SPICE doesn't understand matrices in its input files anyway, AFAIK, so you'd have to write the silly things out longhand anyway.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

It's not that hard. Remember orthogonality ?:-)

Here's how S-parameters are handled in Spice...

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h-parameters can be done the same way. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

We're actually in violent agreement, then. No matrices that I could see. (I like the behavioural model for putting in S parameters. SPICE is just a glorified nonlinear sparse ODE solver, after all.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

Well, in a twisted way that kind of makes my point: h-parameters are introduced so that the student can use linear analysis to get a feel for how circuits work. You already knew.

One of the conceptual models that I find useful is a pair of back-to-back diodes, with a dependent current source around the B-C junction, possibly with appropriate base spreading resistance if that's going to matter. It does a good enough job of predicting most of the pertinent linearized parameters at any one operating point, and it makes it easy to visualize what's going to happen if anything reverse biases.

("Good enough job" is defined here as "kinda in the center of the variation you can expect anyway").

I honestly feel that one should not do SPICE modeling unless you _really_ understand the circuit: otherwise you'll miss something important.

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com
Reply to
Tim Wescott

are

Yep. My point, exactly. To ease my head-scratching processes I've developed a number of "gadgets" for PSpice that make solving (and displaying) such solutions a piece-a-cake.

And LTspice is next. I've finally cracked the 4046 (in terms of behavioral modeling) and will release a first pass on the VCO portion shortly. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson
[snip]

Spice is the "check" portion of a design. Spice doesn't pick, or place, any of the components I place on a schematic... I do.

Spice can do process corners and/or Monte Carlo in minutes. A human might _never_ be able to discover all possible situations. ...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     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Ah! That's the point. But when teachers don't supplement the text books, you find yourself worse off than between the devil and the deep blue sea. ...

Yes, I thought asymmetrical diodes represented the circuit better.

Reply to
rajibbandopadhyay

Sorry I forgot to emphasise how important this comment is! So, it is better that instead of remembering the formulae of h-parameters, we do the analysis in the same way as h-parameters are reduced using simplistic logic. This at least sound logical :)

Reply to
Rajib Kumar Bandopadhyay

To get S11, I usually put the DUT in one side of a Wheatstone bridge, which is exactly the way some VNAs do it in real life. Apply 'AC 2' to the top of the bridge and get S11 as the voltage across. It's very similar to the approach in your reference, but it uses only one AC source. It's so simple I never bothered to encapsulate it in subcircuits.

Jeroen Belleman

Reply to
Jeroen Belleman

(Today I realized that I answered this privately to the OP -and not to the group. Here are my thoughts on this:)

Hybrid parameters are just one of several representations for two-ports. Working with the conventional port variables V1, I1, V2, I2 there are 6 combinations of the independent variables, each one giving one specific family. In practice, one family of parameters may be easier to measure, or a given family may not exist.

So, your question should be rephrased as: is the two-port concept useful for design? And the short response is yes.

Pere

Reply to
o pere o

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