Microstrip wideband AC coupling...

J

John Larkin

Guest
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.
Click to expand...

Comes up 500 at the moment.

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
 
On Tue, 7 Dec 2021 16:05:09 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.


Comes up 500 at the moment.

Cheers

Phil Hobbs
Click to expand...

Strange; that link used to work.

Dropbox used to just work. They have fancied it up and mostly broke
it.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
On Tue, 07 Dec 2021 11:16:37 -0800, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.
Click to expand...

Where do you find these sideways capacitors ?
 
boB wrote:
On Tue, 07 Dec 2021 11:16:37 -0800, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.


Where do you find these sideways capacitors ?
Click to expand...

Digikey. Search on \"0204 capacitor\" and 98 part numbers come up,
including this one:

<https://www.digikey.com/en/products/detail/murata-electronics/LLL153C80G105ME21D/4905678>

0.47 uF, 4V, with most of the capacitance remaining at the rated
voltage, 3 cents in reels.

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
 
John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.
Click to expand...

Dropbox found the picture again. It does look like the 0204 is a good
fit to the 50-ohm line. Do you have the TDRs handy?

Thanks

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
 
Am 08.12.21 um 04:53 schrieb Phil Hobbs:
John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.


Dropbox found the picture again.  It does look like the 0204 is a good
fit to the 50-ohm line.  Do you have the TDRs handy?
Click to expand...

How wide a 50 Ohm line is depends on eps-r of the board and the
stackup. We got excellent results for the eye diagrams @ 10 GBps
with 0402 AVX capacitors > 10 years ago.

And I wonder why the CV product is so much worse for the short &
fat capacitors vs. the normal slim & long ones.

I have a lot of 0612 10u 6V3 here, DK 445-4072-1-ND, never used them.

cheers, Gerhard
 
On Tue, 7 Dec 2021 22:53:21 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.


Dropbox found the picture again. It does look like the 0204 is a good
fit to the 50-ohm line. Do you have the TDRs handy?

Thanks

Phil Hobbs
Click to expand...

https://www.dropbox.com/sh/w4qqa260o7wu4vg/AADWbTl1sr3ZBEzha1TIlvIla?dl=0

The caps are at cm 7 in the upper/TDR trace. The Mueller edge-launch
SMA connectors are worse than the caps. We did nail 50 ohms pretty
good on this one.



--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
John Larkin wrote:
On Tue, 7 Dec 2021 22:53:21 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
https://www.dropbox.com/s/tugwe4mnoj2ri80/Z508_AC_Coupling.jpg?raw=1

0306 cap, capacitive bump. 0603 cap, inductive bump. No surprise that
the 0204 is best. In the 25 ps sort of domain, on FR4, there\'s no need
to buy exotic caps.

That 0204 is a 0.47 uF 16 volt cap. With 9 volts DC bias from my
distributed amplifier, it loses 80% of its capacitance.


Dropbox found the picture again. It does look like the 0204 is a good
fit to the 50-ohm line. Do you have the TDRs handy?

Thanks

Phil Hobbs

https://www.dropbox.com/sh/w4qqa260o7wu4vg/AADWbTl1sr3ZBEzha1TIlvIla?dl=0

The caps are at cm 7 in the upper/TDR trace. The Mueller edge-launch
SMA connectors are worse than the caps. We did nail 50 ohms pretty
good on this one.
Click to expand...

Very nice!

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
 
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