RF Black Magic- Eliminating Fringing Capacitance...

[Brent Locher]

On Monday, November 16, 2020 at 12:14:02 PM UTC-5, Gerhard Hoffmann wrote:

Am 16.11.20 um 17:49 schrieb Brent Locher:
On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?

Actually, it affects just about everything via the error correction.
S-parameters, stability criteria ...

Google \"12 term error correction\".

regards, Gerhard

If these minor errors in the \"open\" calibration are going to make a difference in what he is doing then he is designing a very fragile circuit. Not to say he is not designing a fragile circuit. But if you are not designing a fragile circuit then do not get wrapped about the axle over this.

 

[server]

On Mon, 16 Nov 2020 08:49:59 -0800 (PST), Brent Locher
<blocher@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:
On Sunday, November 15, 2020 at 12:44:38 PM UTC-5, Cursitor Doom wrote:
Gentlemen,

If I may return to the subject of electronics, I\'d like to ask what
exactly is so difficult about making open terminations for calibrating
vector network analysers. I can make up loads from scratch that are
good to over a gig without making any real effort. I can achieve
almost as good results making my own shorts, too. But when it comes to
opens, the nice tight dots I\'m seeing with loads and shorts turns into
an ugly streak; several degress of arc at the left hand edge of the
polar display. I\'m given to understand this phenomenon is due to
\"fringing capacitance\" and it\'s a PITA to correct for. Anyone got any
suggestions?


THanks,

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?

Really, RF parts aren\'t all that repeatable. Mini-Circuits (and
others) change fabs now and then, without warning. Lots of RF parts
don\'t have min/max specs anyhow.

And, no offense intended, RF is fairly fuzzy anyhow. People measure in
dBs, not per cents or PPMs.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Brent Locher]

On Monday, November 16, 2020 at 1:18:51 PM UTC-5, jla...@highlandsniptechnology.com wrote:

On Mon, 16 Nov 2020 08:49:59 -0800 (PST), Brent Locher
blo...@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:
On Sunday, November 15, 2020 at 12:44:38 PM UTC-5, Cursitor Doom wrote:
Gentlemen,

If I may return to the subject of electronics, I\'d like to ask what
exactly is so difficult about making open terminations for calibrating
vector network analysers. I can make up loads from scratch that are
good to over a gig without making any real effort. I can achieve
almost as good results making my own shorts, too. But when it comes to
opens, the nice tight dots I\'m seeing with loads and shorts turns into
an ugly streak; several degress of arc at the left hand edge of the
polar display. I\'m given to understand this phenomenon is due to
\"fringing capacitance\" and it\'s a PITA to correct for. Anyone got any
suggestions?


THanks,

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?
Really, RF parts aren\'t all that repeatable. Mini-Circuits (and
others) change fabs now and then, without warning. Lots of RF parts
don\'t have min/max specs anyhow.

And, no offense intended, RF is fairly fuzzy anyhow. People measure in
dBs, not per cents or PPMs.
--

Actually, Rf parts in the .500-2GHz are very stable (repeatable) and solid these days. remarkably so. There are so many functions built into parts too....for instance, amplifiers are all biased up and matched to 50 ohms. It would be curious to know what he is actually trying to measure to determine if this little bit of phase slide into an open circuit would make any difference or not.

If he is just doing S21 measurements on an amplifier I doubt it matters. If he needs to know this for some reflective oscillator application then the measurement is going to be trumped by his empirical results.

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Cursitor Doom]

On Mon, 16 Nov 2020 08:49:59 -0800 (PST), Brent Locher
<blocher@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:
On Sunday, November 15, 2020 at 12:44:38 PM UTC-5, Cursitor Doom wrote:
Gentlemen,

If I may return to the subject of electronics, I\'d like to ask what
exactly is so difficult about making open terminations for calibrating
vector network analysers. I can make up loads from scratch that are
good to over a gig without making any real effort. I can achieve
almost as good results making my own shorts, too. But when it comes to
opens, the nice tight dots I\'m seeing with loads and shorts turns into
an ugly streak; several degress of arc at the left hand edge of the
polar display. I\'m given to understand this phenomenon is due to
\"fringing capacitance\" and it\'s a PITA to correct for. Anyone got any
suggestions?


THanks,

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?

AFAIK, the overwhelming majority of S11 measurements are not concerned
with phase. S21 certainly is, though.

 

[Cursitor Doom]

On Mon, 16 Nov 2020 18:08:27 +0100, \"Robert Lacoste\"
<see-alciom-dot-com@none.com> wrote:

May be another way to look at the problem : A VNA calibration kit is *not* a
set of perfect open, shorts and loads, but a set of stable references, as
close as possible to open/short/loads, with precisely measured
characteristics. As far as I know, cal kit are always supplied with cal data
(was on a floppy disk in the good old days... I guess they are now on an
Eeprom inside the electronic cal kit).

ISTR that the later HP VNAs certainly did this and also \'recognised\'
when the cal kit being used was one of theirs or not. If it *did* turn
out to be one of theirs, then the accuracy was noticeably better.

 

[John Larkin]

On Mon, 16 Nov 2020 11:18:55 -0800 (PST), Brent Locher
<blocher@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 1:18:51 PM UTC-5, jla...@highlandsniptechnology.com wrote:
On Mon, 16 Nov 2020 08:49:59 -0800 (PST), Brent Locher
blo...@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:
On Sunday, November 15, 2020 at 12:44:38 PM UTC-5, Cursitor Doom wrote:
Gentlemen,

If I may return to the subject of electronics, I\'d like to ask what
exactly is so difficult about making open terminations for calibrating
vector network analysers. I can make up loads from scratch that are
good to over a gig without making any real effort. I can achieve
almost as good results making my own shorts, too. But when it comes to
opens, the nice tight dots I\'m seeing with loads and shorts turns into
an ugly streak; several degress of arc at the left hand edge of the
polar display. I\'m given to understand this phenomenon is due to
\"fringing capacitance\" and it\'s a PITA to correct for. Anyone got any
suggestions?


THanks,

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?
Really, RF parts aren\'t all that repeatable. Mini-Circuits (and
others) change fabs now and then, without warning. Lots of RF parts
don\'t have min/max specs anyhow.

And, no offense intended, RF is fairly fuzzy anyhow. People measure in
dBs, not per cents or PPMs.
--

Actually, Rf parts in the .500-2GHz are very stable (repeatable) and solid these days. remarkably so. There are so many functions built into parts too....for instance, amplifiers are all biased up and matched to 50 ohms. It would be curious to know what he is actually trying to measure to determine if this little bit of phase slide into an open circuit would make any difference or not.

If he is just doing S21 measurements on an amplifier I doubt it matters. If he needs to know this for some reflective oscillator application then the measurement is going to be trumped by his empirical results.

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I use MMICs as wideband pulse amplifiers and TDR them to see the
equivalent input impedance. 50 ohm parts might be 38, might be 65.

The newer self-biasing MMICs have very strange internal bias loops.

Power parts, on their data sheets, usually say \"adjust the DC bias
trimpot until it works.\" I have to do my own DC measurements.

 

[John Larkin]

On Mon, 16 Nov 2020 23:59:47 +0000, Cursitor Doom <cd@noreply.com>
wrote:

On Mon, 16 Nov 2020 08:49:59 -0800 (PST), Brent Locher
blocher@columbus.rr.com> wrote:

On Monday, November 16, 2020 at 11:48:30 AM UTC-5, Brent Locher wrote:
On Sunday, November 15, 2020 at 12:44:38 PM UTC-5, Cursitor Doom wrote:
Gentlemen,

If I may return to the subject of electronics, I\'d like to ask what
exactly is so difficult about making open terminations for calibrating
vector network analysers. I can make up loads from scratch that are
good to over a gig without making any real effort. I can achieve
almost as good results making my own shorts, too. But when it comes to
opens, the nice tight dots I\'m seeing with loads and shorts turns into
an ugly streak; several degress of arc at the left hand edge of the
polar display. I\'m given to understand this phenomenon is due to
\"fringing capacitance\" and it\'s a PITA to correct for. Anyone got any
suggestions?


THanks,

CD
First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.


Actually, I think it only effects S11 (or S22) readings. are your reflection measurements that critical?


AFAIK, the overwhelming majority of S11 measurements are not concerned
with phase. S21 certainly is, though.

I asked MiniCircuits if one of their MMICs inverted the signal or not.
They didn\'t know.

Of course, Darlington mmics invert.

 

[Gerhard Hoffmann]

Am 17.11.20 um 01:24 schrieb John Larkin:

I asked MiniCircuits if one of their MMICs inverted the signal or not.
They didn\'t know.

No. You did not know what to ask. The question makes no sense.
When the MMIC turns the phase by 270° at 5 GHz, does it invert?

> Of course, Darlington mmics invert.

You are thinking DC.
You were given the S-parameters but were unable to interpret.

Gerhard

 

[Steve Wilson]

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 17.11.20 um 01:24 schrieb John Larkin:


I asked MiniCircuits if one of their MMICs inverted the signal or not.
They didn\'t know.

No. You did not know what to ask. The question makes no sense.
When the MMIC turns the phase by 270° at 5 GHz, does it invert?

Of course, Darlington mmics invert.

You are thinking DC.
You were given the S-parameters but were unable to interpret.

Gerhard

https://www.minicircuits.com/pdfs/mcl_modelith_2017.pdf



--
Science teaches us to trust. - sw

 

[server]

On Tue, 17 Nov 2020 04:29:11 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 17.11.20 um 01:24 schrieb John Larkin:


I asked MiniCircuits if one of their MMICs inverted the signal or not.
They didn\'t know.

No. You did not know what to ask. The question makes no sense.
When the MMIC turns the phase by 270° at 5 GHz, does it invert?

Of course, Darlington mmics invert.

You are thinking DC.
You were given the S-parameters but were unable to interpret.

Gerhard

No, I was just trying to see if the MiniCircuits engineer understood
the part.

I work in time, not phase.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Steve Wilson]

jlarkin@highlandsniptechnology.com wrote:

On Tue, 17 Nov 2020 04:29:11 +0100, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 17.11.20 um 01:24 schrieb John Larkin:


I asked MiniCircuits if one of their MMICs inverted the signal or
not.
They didn\'t know.

No. You did not know what to ask. The question makes no sense.
When the MMIC turns the phase by 270° at 5 GHz, does it invert?

Of course, Darlington mmics invert.

You are thinking DC.
You were given the S-parameters but were unable to interpret.

Gerhard

No, I was just trying to see if the MiniCircuits engineer understood
the part.

I work in time, not phase.

270° at 5 GHz is phase.



--
Science teaches us to trust. - sw

 

[Gerhard Hoffmann]

Am 16.11.20 um 17:48 schrieb Brent Locher:

First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.

This here is an amplifier made by a regular of s.e.d. who is currently
badly missed.
<
https://www.flickr.com/photos/137684711@N07/49922062651/in/album-72157662535945536/
>

The amplifier is potentially unstable. Between 100 KHz and 50 MHz, the
real part of the input impedance is negative. The rest of the input
impedance is a small capacitor. If you connect anything inductive to
the input, the amplifier will oscillate. The measured phase angle will
tell the oscillation frequency.

The proper measurement to diagnose this would be a measurement of S11.
From a different amplifier that shares the same problem:
<
https://www.flickr.com/photos/137684711@N07/34701106245/in/album-72157662535945536/
>
Around Marker2, the trajectory leaves the unit circle, meaning that
if you send a wave into that port at these frequencies, a bigger wave
will come back, the effect of the negative real part.



BTW, I have given up to cure that kind of amplifier. I have made one
without feedback around the FET. Everything else either loses a lot
of bandwidth to the point of being uninteresting or plays games with
parameters that are badly defined. :-(

Gerhard

 

[Gerhard Hoffmann]

Am 17.11.20 um 05:05 schrieb Steve Wilson:
erhard

No, I was just trying to see if the MiniCircuits engineer understood
the part.

I work in time, not phase.

270° at 5 GHz is phase.

Does it invert?

Make up your mind! Half convinced does not count

Gerhard

 

[Steve Wilson]

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 17.11.20 um 05:05 schrieb Steve Wilson:
erhard

No, I was just trying to see if the MiniCircuits engineer understood
the part.

I work in time, not phase.

270° at 5 GHz is phase.

Does it invert?

Make up your mind! Half convinced does not count

Gerhard

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus inverter),
at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.


--
Science teaches us to trust. - sw

 

[Gerhard Hoffmann]

Am 17.11.20 um 06:34 schrieb Steve Wilson:

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus inverter),
at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.

No, not really. My, nowadays somewhat historic 2.5 GHz 1152A probes are
the pure joy (apart of running somewhat hot for my fingers). Having
the deeper pockets of my customers, something faster should be possible.

But, that all does not answer the question: DOES IT INVERT???
I admit, 270° is hard to decide, even when one assumes an error band.

Cheers, Gerhard

 

[Steve Wilson]

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 17.11.20 um 06:34 schrieb Steve Wilson:

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus
inverter), at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.

No, not really. My, nowadays somewhat historic 2.5 GHz 1152A probes
are the pure joy (apart of running somewhat hot for my fingers).
Having the deeper pockets of my customers, something faster should be
possible.

But, that all does not answer the question: DOES IT INVERT???
I admit, 270° is hard to decide, even when one assumes an error band.

Cheers, Gerhard

The 1152A is only 2.5GHz, or 1.3GHz with the 54845A and 500MHz with the
54810A. The probe is useless at 5GHz.

The input capacity is 0.6pf, or 106 ohms at 2.5GHz. This will cause
significant error in 50 Ohms:

1/(2*pi*2.5e9*0.6e-12) = 106

The propagation delay is 7.5ns. Getting two matched to less than 50ps
will be difficult.

Reference:
http://literature.cdn.keysight.com/litweb/pdf/01152-97002.pdf

Don\'t try to measure a dut when the system bandwidth is about the same as
the dut. Use a system with a bandwidth that is much higher.

I would prefer a wideband 10:1 purely resistive probe. Attenuators using
distributed resistors are useful up to 30GHz:

https://www.jstage.jst.go.jp/article/elex/13/10/13_13.20160321/_pdf



--
Science teaches us to trust. - sw

 

[Brent Locher]

On Monday, November 16, 2020 at 11:36:24 PM UTC-5, Gerhard Hoffmann wrote:

Am 16.11.20 um 17:48 schrieb Brent Locher:


First off, this calibration \"error\" is going to only effect phase readings on either S21 or S11. Is this several degrees of phase error something that is important to you? If not then move on.
This here is an amplifier made by a regular of s.e.d. who is currently
badly missed.

https://www.flickr.com/photos/137684711@N07/49922062651/in/album-72157662535945536/


The amplifier is potentially unstable. Between 100 KHz and 50 MHz, the
real part of the input impedance is negative. The rest of the input
impedance is a small capacitor. If you connect anything inductive to
the input, the amplifier will oscillate. The measured phase angle will
tell the oscillation frequency.

The proper measurement to diagnose this would be a measurement of S11.
From a different amplifier that shares the same problem:

https://www.flickr.com/photos/137684711@N07/34701106245/in/album-72157662535945536/

Around Marker2, the trajectory leaves the unit circle, meaning that
if you send a wave into that port at these frequencies, a bigger wave
will come back, the effect of the negative real part.



BTW, I have given up to cure that kind of amplifier.

That is my point. If you need to have S11 measured so precise you are probably playing with a very sensitive circuit. In your case you gave up on it.. In the 0.5-2GHz range there are so many fantastic parts available that take care of all the finickiness. The OP has not yet stated why he needs such a precise measurement. If it is a theoretical thing then so be it.


I have made one

without feedback around the FET. Everything else either loses a lot
of bandwidth to the point of being uninteresting or plays games with
parameters that are badly defined. :-(

Gerhard

 

[Gerhard Hoffmann]

Am 17.11.20 um 08:04 schrieb Steve Wilson:

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 17.11.20 um 06:34 schrieb Steve Wilson:

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus
inverter), at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.

No, not really. My, nowadays somewhat historic 2.5 GHz 1152A probes
are the pure joy (apart of running somewhat hot for my fingers).
Having the deeper pockets of my customers, something faster should be
possible.

But, that all does not answer the question: DOES IT INVERT???
I admit, 270° is hard to decide, even when one assumes an error band.

Cheers, Gerhard

The 1152A is only 2.5GHz, or 1.3GHz with the 54845A and 500MHz with the
54810A. The probe is useless at 5GHz.

The input capacity is 0.6pf, or 106 ohms at 2.5GHz. This will cause
significant error in 50 Ohms:> 1/(2*pi*2.5e9*0.6e-12) = 106

The propagation delay is 7.5ns. Getting two matched to less than 50ps
will be difficult.

It was not me who brought up \"Probes\" at all. They have absolutely
nothing to do with fringing capacitance on a OPEN reference for
a vector network analyzer.

In fact, I\'m the one with the VNA and VNA-controlled calibration kit.

Matching probe delays is not difficult, but it does not make sense
to match probe delay to 50ps when the scope risetime is 150 ps.
And if you insist, you can correct the delays
under SETUP -> CHANNEL -> PROBES with 1 ps resolution, forth and back.

Also, the BW of a a 1152A is always 2.5 GHz. It does not get less if you
plug it on an inferior scope. It cannot make the scope faster. I do not
have an inferior scope, but also the same probe with N/SMA connector
for use with other devices. ( 54701A )

The 0.6 pF is essential because the length of the ground strap
plays a much lesser role than with the usual 10 pF probes, even at 1:10.
It pushes the annoying series resonance up in frequency where it
is much less excited from LVC and other fast CMOS risetimes.

The biggest drawback is that it cannot switch to AC coupling, so you
constantly have to correct the Y position.

Reference:
http://literature.cdn.keysight.com/litweb/pdf/01152-97002.pdf

Oh, thanks, but I have the real thing in everyday use on channel
1 and 2 of the scope. 3 is a 500 MHz passive probe and 4 a SMA cable.

Don\'t try to measure a dut when the system bandwidth is about the same as
the dut. Use a system with a bandwidth that is much higher.

I would prefer a wideband 10:1 purely resistive probe.

I have one from TEK, never ever found the hyped 450 Ohm resistor useful
for anything. I would not note it if it walked away.

Cheers, Gerhard

 

[Phil Hobbs]

On 11/17/20 12:58 AM, Gerhard Hoffmann wrote:

Am 17.11.20 um 06:34 schrieb Steve Wilson:

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus inverter),
at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.

No, not really. My, nowadays somewhat historic 2.5 GHz 1152A probes are
the pure joy (apart of running somewhat hot for my fingers). Having
the deeper pockets of my customers, something faster should be possible.

But, that all does not answer the question: DOES IT INVERT???
I admit, 270° is hard to decide, even when one assumes an error band.

Cheers, Gerhard

Nah, if it were 270 degrees noninverting right at its output, you\'d have
a 3-pole rolloff.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Tue, 17 Nov 2020 10:00:32 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 11/17/20 12:58 AM, Gerhard Hoffmann wrote:
Am 17.11.20 um 06:34 schrieb Steve Wilson:

A phase shift of 270 degrees at 5GHz could be caused by a propagation
delay of 50 picoseconds through the amplifier.

Calculations:

1/5e9 = 0.2ns = 200ps
180 degrees = 100ps
270 degrees = 100ps + 50ps

50ps is reasonable for two transistors, (emitter follower plus inverter),
at 5GHz.

Probing a circuit to minimize time shift error is difficult at 5GHz.

Matching two probes at 5GHz is difficult.

No, not really. My, nowadays somewhat historic 2.5 GHz 1152A probes are
the pure joy (apart of running somewhat hot for my fingers). Having
the deeper pockets of my customers, something faster should be possible.

But, that all does not answer the question: DOES IT INVERT???
I admit, 270° is hard to decide, even when one assumes an error band.

Cheers, Gerhard


Nah, if it were 270 degrees noninverting right at its output, you\'d have
a 3-pole rolloff.

Cheers

Phil Hobbs

Here\'s the TDR/TDT response of a GALI-59, a classic Darlington mmic:

https://www.dropbox.com/s/uyvhwi5jplo36ym/Gali-59_TDR.JPG?raw=1

Of one wants maximum pulse amplitude for narrow pulses, you can pull
the input up or down to bias the output off-center. It may surprise
the RF boys that not all waveforms are symmetric. S-parameters are
small-signal linear, which isn\'t terribly interesting for pulse work.
S11 cares a lot about the load too, since the input impedance (and the
DC bias!) is mostly set by the feedback resistor from the output.



This is a GVA-63, which is a newfangled self-biasing part:

https://www.dropbox.com/s/dhmmakm4xs1stuo/GVA-63_TDR.jpg?raw=1

The s-param charts for these typically cut off on the low-frequency
end to hide what\'s going on. Just apply 5 volts through an inductor
and don\'t ask questions.

Maximum voltage swing is another thing that has to be found by
experiment.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard