# How to determine Zin, Yout for RF transistor, from A parameters

Started by May 6, 2017
```Could some RGF/microwave guru on this newsgroup
a ONSemi RF transistor, with the S parameters
listed for various frequencies. What would be
a quick and easy(that I can code as a simple
C program) way to convert these to the
corresponding Zin and Yout. Thanks in
```
```wrote in message

>Could some RGF/microwave guru on this newsgroup
>a ONSemi RF transistor, with the S parameters
>listed for various frequencies. What would be
>a quick and easy(that I can code as a simple
>C program) way to convert these to the
>corresponding Zin and Yout. Thanks in

Why?

Try and find the spice model, and do everything in spice.

One of the remain reasons for stuff like S parameters, was simply that it
was easier to measure than other ones in the distant past. Its simply all
irrelevant now. We have simulation tools.

S parameters are way too limiting for optimum design. Usually, they are only
specified for one or a few current/voltage sets, and they are only useful at
all for linear analysis. This is a disaster for decent optimum production
design.s

S parameter design for transistor circuits is, essentially, a legacy
claptrap rut, that many just can't get out off.

A good spice model will allow you do accurately design over the whole range
of operating currents and voltages including the required transient, real
world large signals that the circuit is actually being used for.

-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

```
```You can do it with a spreadsheet.
Checkout Rfcafe.com
M
```
```>S parameter design for transistor circuits is, essentially, a legacy
>claptrap rut, that many just can't get out off.

You're obviously not an RF guy.  S parameters let you calculate analytically things like the stability boundary, active vs passive regions, maximum available gain, and so on.

Smith charts are super fast and intuitive, as well.

A single analytical result is worth more than a stack of simulations. There are cases that are too hard analytically, but one-transistor microwave amps are not among them.

Cheers

Phil Hobbs

```
```Sadly, a ton of transistors just don't give that info.

Some don't even give s-params, or their LF equivalents (junction C's,
internal resistances, etc.).

The OP wasn't exactly specific...

It's nice to just keep shopping for a part that does, but if this is going
deep into the rarefied territory of RF (the OP wasn't exactly specific :) ),
you can be SOL very easily.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

"Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> wrote in message
news:pKqdnS_JAfH24JDEnZ2dnUU7-L3NnZ2d@giganews.com...
> wrote in message
>
>>Could some RGF/microwave guru on this newsgroup
>>a ONSemi RF transistor, with the S parameters
>>listed for various frequencies. What would be
>>a quick and easy(that I can code as a simple
>>C program) way to convert these to the
>>corresponding Zin and Yout. Thanks in
>
> Why?
>
> Try and find the spice model, and do everything in spice.
>
> One of the remain reasons for stuff like S parameters, was simply that it
> was easier to measure than other ones in the distant past. Its simply all
> irrelevant now. We have simulation tools.
>
> S parameters are way too limiting for optimum design. Usually, they are
> only specified for one or a few current/voltage sets, and they are only
> useful at all for linear analysis. This is a disaster for decent optimum
> production design.s
>
> S parameter design for transistor circuits is, essentially, a legacy
> claptrap rut, that many just can't get out off.
>
> A good spice model will allow you do accurately design over the whole
> range of operating currents and voltages including the required transient,
> real world large signals that the circuit is actually being used for.
>
> -- Kevin Aylward
> http://www.anasoft.co.uk - SuperSpice
> http://www.kevinaylward.co.uk/ee/index.html

```
```https://en.wikipedia.org/wiki/Two-port_network#Scattering_parameters_.28S-parameters.29

Curiously, they don't provide the exact formulas relating s-params to the
other types of network equations.  But between the related articles, it
looks that there's enough information to solve for it.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

<dakupoto@gmail.com> wrote in message
> Could some RGF/microwave guru on this newsgroup
> a ONSemi RF transistor, with the S parameters
> listed for various frequencies. What would be
> a quick and easy(that I can code as a simple
> C program) way to convert these to the
> corresponding Zin and Yout. Thanks in

```
```On 06/05/2017 04:50, dakupoto@gmail.com wrote:
> Could some RGF/microwave guru on this newsgroup
> a ONSemi RF transistor, with the S parameters
> listed for various frequencies. What would be
> a quick and easy(that I can code as a simple
> C program) way to convert these to the
> corresponding Zin and Yout. Thanks in
>

https://www.dropbox.com/s/l06sp8jr0rdd46s/Sconvert.pdf?dl=0
```
```On a sunny day (Sat, 6 May 2017 11:24:14 -0500) it happened "Tim Williams"
<tiwill@seventransistorlabs.com> wrote in <oekt4r\$aoj\$1@dont-email.me>:

>Sadly, a ton of transistors just don't give that info.
>
>Some don't even give s-params, or their LF equivalents (junction C's,
>internal resistances, etc.).
>
>The OP wasn't exactly specific...
>
>It's nice to just keep shopping for a part that does, but if this is going
>deep into the rarefied territory of RF (the OP wasn't exactly specific :) ),
>you can be SOL very easily.
>
>Tim
>
>--
>Seven Transistor Labs, LLC
>Electrical Engineering Consultation and Contract Design
>Website: http://seventransistorlabs.com
>
>
>"Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> wrote in message
>news:pKqdnS_JAfH24JDEnZ2dnUU7-L3NnZ2d@giganews.com...
>> wrote in message
>>
>>>Could some RGF/microwave guru on this newsgroup
>>>a ONSemi RF transistor, with the S parameters
>>>listed for various frequencies. What would be
>>>a quick and easy(that I can code as a simple
>>>C program) way to convert these to the
>>>corresponding Zin and Yout. Thanks in
>>
>> Why?
>>
>> Try and find the spice model, and do everything in spice.
>>
>> One of the remain reasons for stuff like S parameters, was simply that it
>> was easier to measure than other ones in the distant past. Its simply all
>> irrelevant now. We have simulation tools.
>>
>> S parameters are way too limiting for optimum design. Usually, they are
>> only specified for one or a few current/voltage sets, and they are only
>> useful at all for linear analysis. This is a disaster for decent optimum
>> production design.s
>>
>> S parameter design for transistor circuits is, essentially, a legacy
>> claptrap rut, that many just can't get out off.
>>
>> A good spice model will allow you do accurately design over the whole
>> range of operating currents and voltages including the required transient,
>> real world large signals that the circuit is actually being used for.
>>
>> -- Kevin Aylward
>> http://www.anasoft.co.uk - SuperSpice
>> http://www.kevinaylward.co.uk/ee/index.html

OK, many people had a go...
Apart from mutilati I mean simulations, and S parameters that I had to do over and over in school
and never used after that,
I VERY STRONGLY RECOMMEND JUST BUYING SOME OF THOSE DEVICES,
MAKING SOME TEST CIRCUITS,
BUILD AN OSCILLATOR, 1 STAGE AMP, ETC, GET THE CURRENT VERSUS VOLTAGE
AND DO NOT HAVE FEAR TO KILL ONE ON MORE, GET THE FEEL OF IT.

These days people run simulations, and really they remind me of NASA,
in the sense that when NASA detects a new planet,
then same day they have an artist impression on their site, sometimes complete with grass, lakes, etc etc..
Von Braun in the sixties build rockets,
no computers at that time, he did get US to the moon and back.
He KNEW (he and some other German engineers that were captured with him) his stuff.
HANDS ON.

It is the same with programming, now people ask: 'Can I do this in Python?'
Well don't you think you should at least know the hardware,
you know, those little flips and flops,
and try some asm, it is actually SIMPLER than Python, more powerful, MUCH more powerful,
and several orders of magnitude faster
so you can do the same or better in a little micro with kB memory and one core

Operating systems and browsers go the same way.
[LT]spice is a joke if it comes to real RF, and normal circuits too.
it is all about layout, and yes there are programs for that too.

As to NASA, Hollywood makes much better artist impressions,
getting so good it is hard to tell what is real and not, not your old puppet show, I was amazed by 'the golden compass'
happened to see it on TV, looked it up, indeed a prize winner.

Long time ago, when first transistors came on the market here (1958?) I remember asking one for my birthday.
Actually got one, PNP Ge, it died rather soon, but man did I learn a lot.

Hell even if you spice it all and cannot handle the soldering iron to make a test circuit what good is it.
And even if your spice works, it may well not in reality.
Welcome to the matrix, and now they wonder why they cannot go to mars.

PS and sometimes even the things do not meet spec, I remember a specific case of VFET.

AND on top of that, if you have your spice working, you have NOTHING,
it is all illusion like that movie, and no planets to walk on.
While I have a working prototype device.

It is all illusions I recall, I really don't know tronix at all.
In the human neural net, you need that configured, and the ONLY way is practical experience with REAL
world stuff.
You may have the math to catch the ball, but that does not mean you can play in major league.
You may be a top player, but have no clue about physics and math.

Maybe one day we will be able to transfer our neural net weights and configuration to
some system, and it would be as smart (or as stupid).
Or to others.

```
```On Sat, 6 May 2017 11:24:14 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>Sadly, a ton of transistors just don't give that info.

You're lucky if you get any DC curves. Or capacitances. I wind up
measuring that stuff, but it's not enough for a high-speed Spice
model.

--

John Larkin         Highland Technology, Inc

lunatic fringe electronics

```
```On 05/06/2017 12:19 PM, pcdhobbs@gmail.com wrote:
>> S parameter design for transistor circuits is, essentially, a legacy
>> claptrap rut, that many just can't get out off.
>
> You're obviously not an RF guy.  S parameters let you calculate analytically things like the stability boundary, active vs passive regions, maximum available gain, and so on.
>
> Smith charts are super fast and intuitive, as well.

If you know how to use a Smith chart you can design an impedance
matching network for same amp in about 5 minutes that would take you the
better part of an hour to grunge thru on paper

```