Nanoamp calibrator again

Phil Hobbs wrote:
> Joerg wrote:
>> Phil Hobbs wrote:
>>> Fred Abse wrote:
>>>> On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
>>>>
>>>>>    OOPS! tried the LTC program and got the following errors:
>>>>> Questionable use of curly braces in "symattr spiceline rser=0.005
>>>>> lser={lcap}"
>>>>>      Error: undefined symbol in: "[lcap]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {rbi}"
>>>>>      Error: undefined symbol in: "[rbi]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Circuit: Version 4
>>>>>
>>>>> Fatal Error: Multiple instances of "Flag"
>>>>>    Maybe one of the problems was that all of the files were in a folder
>>>>> on another drive.
>>>> Ran first time for me.
>>>
>>> I posted a rebiased version that runs off +5V and gets the edge
>>> artifacts down to something reasonable.
>> I still get "Couldn't find symbol npnsub".
> 
> The .asy file is there on the webpage--the LTspice NPN symbol doesn't
> work with a subcircuit, so I had to make another one.
> 

Here's the trick how to do that: Place the standard symbol for NPN,
shift-rightclick into it, change the prefix to X and the value to
BFP640FESD, then copy the subcircuit into the SPICE file via the command
text box. That's it. Just tried that with Q4 in your circuit -> woiks.


>>  It uses single-ended drive for
>>> the pHEMT differential pair Z2/Z3, in order to prevent capacitive gate
>>> current in Z3 from corrupting the output.  Using ten 39 pF caps in
>>> parallel reduces the equivalent series inductance, and adding an RLC
>>> filter to the output makes the transition a lot cleaner.
>>>
>>> The output as before is I(C5).  The simulation shows all sorts of
>>> ripples at up to 12 GHz elsewhere in the circuit, which I really don't
>>> think are real.  (The pHEMTs are that fast at 20 mA of drain current,
>>> but surely not at 70 uA.)
>>>
>>> Anyway, I think this can be made to work, assuming that the layout
>>> person knows something about RF.
>>>
>> And think about tricks like meander-back to reduce inductance.
> 
> Care to expound?
> 

Basically the old Ayton-Perry trick but only half turn. Not sure if you
have HoJo's book but if not, this works as illustration what you'd have
without any tricks:

http://www.sigcon.com/Pubs/news/6_09.htm

Take the 0402 side case but place the vias in the pads. Should get you
under 0.2nH. Now place two of those, super-close to each other, run the
signal trace down the middle of them (sideways), connect one on the left
and one on the right. GND would then be vice versa, first right, then
left. Now the loops are opposing and so are the parasitic magnetic
fields, helping the cancel each other. Well, to some extent.

There are also caps with four pads but not sure how low they'll get you
down in inductance.

You can also get 01005 size caps from Murata and if still not good
enough parallel a few, then the parasitic inductance is miniscule. But
you'll probably need lasered vias in order to have them in-pad, I don't
think those can be drilled.

Have the ground plane right underneath and use a very thin board so the
via lengths are small. Because they niow become a significant
contributor to the parasitic inductance.

With stuff like this you either have to sit next to the layouter or do
the layout yourself.

Back to the darn irrigation valve now, but this time I'll first test it
in the driveway. If you hear *POP* from out west then the contraption I
made to pressurize it has burst.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Phil Hobbs wrote:
> Joerg wrote:
>> Robert Baer wrote:
>>> John Larkin wrote:
>>>> On Thu, 31 May 2012 15:07:58 -0400, Phil Hobbs
>>>> <pcdhSpamMeSenseless@electrooptical.net>  wrote:
>>>>
>>>>> So, I had a chance to get back to that calibration gizmo for my biochip
>>>>> front end amplifier (1 nA at the shot noise limit in a 100-MHz BW).
>>>>>
>>>>> It turns out that it's possible to do a very nice job, assuming that the
>>>>> integration cap (C1 in the schematic) has zero inductance, but as much
>>>>> as 0.05 nH blows it out of the water.  (Should have thought of that, of
>>>>> course, but oh well.)
>>>>>
>>>>> Try running the sim at
>>>>> http://electrooptical.net/www/sed/sed.html#Calibrator and see.
>>>>>
>>>>> With zero inductance in series with the cap, it switches in well under 1
>>>>> ns.  (The pHEMT diff pair switches in ~100 ps, and faster if I use more
>>>>> source current.)  There's a certain amount of cruft in this schematic,
>>>>> e.g. I probably wouldn't bother with a current source to drive the
>>>>> sources of the pHEMTs, but you know how these things accumulate as you
>>>>> go along.
>>>>>
>>>>> Any bright ideas?
>>>>>
>>>>> Thanks
>>>>>
>>>>> Phil Hobbs
>>>> "Couldn't find symbol npnsub"
>>>>
>>>>
>>>   Look harder..
>> It's usually best to include all non-standard models right inside the
>> SPICE file and then declare a regular parts a subcircuit.
> 
> 
> The BFP640FESD model is sort of large and complicated, and I don't think
> you can put a symbol in a .asc file--can you?
> 

You don't have to, it's much easier than that. See my other post from a
few minutes ago.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Joerg wrote:
> Phil Hobbs wrote:
>> Joerg wrote:
>>> Phil Hobbs wrote:
>>>> Fred Abse wrote:
>>>>> On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
>>>>>
>>>>>>    OOPS! tried the LTC program and got the following errors:
>>>>>> Questionable use of curly braces in "symattr spiceline rser=0.005
>>>>>> lser={lcap}"
>>>>>>      Error: undefined symbol in: "[lcap]"
>>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>>      Error: undefined symbol in: "[lbead]"
>>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>>> Questionable use of curly braces in "symattr value {rbi}"
>>>>>>      Error: undefined symbol in: "[rbi]"
>>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>>      Error: undefined symbol in: "[lbead]"
>>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>>      Error: undefined symbol in: "[lbead]"
>>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>>      Error: undefined symbol in: "[lbead]"
>>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>>      Error: undefined symbol in: "[lbead]"
>>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>>> Circuit: Version 4
>>>>>>
>>>>>> Fatal Error: Multiple instances of "Flag"
>>>>>>    Maybe one of the problems was that all of the files were in a folder
>>>>>> on another drive.
>>>>> Ran first time for me.
>>>> I posted a rebiased version that runs off +5V and gets the edge
>>>> artifacts down to something reasonable.
>>> I still get "Couldn't find symbol npnsub".
>> The .asy file is there on the webpage--the LTspice NPN symbol doesn't
>> work with a subcircuit, so I had to make another one.
>>
> 
> Here's the trick how to do that: Place the standard symbol for NPN,
> shift-rightclick into it, change the prefix to X and the value to
> BFP640FESD, then copy the subcircuit into the SPICE file via the command
> text box. That's it. Just tried that with Q4 in your circuit -> woiks.
> 

PS: Right-click is enough, no need to press the shift key. I was just
used to that from another program

[...]

-- 
Regards, Joerg

http://www.analogconsultants.com/

Bill Sloman wrote:

> On Jun 2, 6:16 pm, Fred Abse <excretatau...@invalid.invalid> wrote:
> 
>>On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
>>
>>>   OOPS! tried the LTC program and got the following errors:
>>>Questionable use of curly braces in "symattr spiceline rser=0.005
>>>lser={lcap}"
>>>     Error: undefined symbol in: "[lcap]"
>>>Questionable use of curly braces in "symattr value {lbead}"
>>>     Error: undefined symbol in: "[lbead]"
>>>Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>     Error: undefined symbol in: "[rpbead]"
>>>Questionable use of curly braces in "symattr value {rbi}"
>>>     Error: undefined symbol in: "[rbi]"
>>>Questionable use of curly braces in "symattr value {lbead}"
>>>     Error: undefined symbol in: "[lbead]"
>>>Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>     Error: undefined symbol in: "[rpbead]"
>>>Questionable use of curly braces in "symattr value {lbead}"
>>>     Error: undefined symbol in: "[lbead]"
>>>Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>     Error: undefined symbol in: "[rpbead]"
>>>Questionable use of curly braces in "symattr value {lbead}"
>>>     Error: undefined symbol in: "[lbead]"
>>>Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>     Error: undefined symbol in: "[rpbead]"
>>>Questionable use of curly braces in "symattr value {lbead}"
>>>     Error: undefined symbol in: "[lbead]"
>>>Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>     Error: undefined symbol in: "[rpbead]"
>>>Circuit: Version 4
>>
>>>Fatal Error: Multiple instances of "Flag"
>>>   Maybe one of the problems was that all of the files were in a folder
>>>on another drive.
>>
>>Ran first time for me.
> 
> 
> Lucky you. I just got a long string of error messages, suggesting that
> whatever end-of-line symbol Phil uses in his longer Spice command
> strings isn't recognised as such by my version of LTSpice.
> 
> --
> Bill Sloman, Nijmegen
It's all about the <CR>/<LF> issues for the most part.

  most of the time, that can be fixed, copy and paste in note pad, and 
set the line returns. Move that into spice afterwards.

  These browsers don't lend themselves to generating plan ASCII text 
very well, especially of you are moving from uni-code text.

  But then again, it could be some other problem with just incompatible 
scripts.

jamie..

On Jun 2, 3:50=A0pm, Joerg <inva...@invalid.invalid> wrote:
> Phil Hobbs wrote:
> > Fred Abse wrote:
> >> On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
>
> >>> =A0 =A0OOPS! tried the LTC program and got the following errors:
> >>> Questionable use of curly braces in "symattr spiceline rser=3D0.005
> >>> lser=3D{lcap}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lcap]"
> >>> Questionable use of curly braces in "symattr value {lbead}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> >>> Questionable use of curly braces in "symattr spiceline rpar=3D{rpbead=
}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> >>> Questionable use of curly braces in "symattr value {rbi}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rbi]"
> >>> Questionable use of curly braces in "symattr value {lbead}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> >>> Questionable use of curly braces in "symattr spiceline rpar=3D{rpbead=
}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> >>> Questionable use of curly braces in "symattr value {lbead}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> >>> Questionable use of curly braces in "symattr spiceline rpar=3D{rpbead=
}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> >>> Questionable use of curly braces in "symattr value {lbead}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> >>> Questionable use of curly braces in "symattr spiceline rpar=3D{rpbead=
}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> >>> Questionable use of curly braces in "symattr value {lbead}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> >>> Questionable use of curly braces in "symattr spiceline rpar=3D{rpbead=
}"
> >>> =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> >>> Circuit: Version 4
>
> >>> Fatal Error: Multiple instances of "Flag"
> >>> =A0 =A0Maybe one of the problems was that all of the files were in a =
folder
> >>> on another drive.
> >> Ran first time for me.
>
> > I posted a rebiased version that runs off +5V and gets the edge
> > artifacts down to something reasonable.
>
> I still get "Couldn't find symbol npnsub".
>
> =A0It uses single-ended drive for
>
> > the pHEMT differential pair Z2/Z3, in order to prevent capacitive gate
> > current in Z3 from corrupting the output. =A0Using ten 39 pF caps in
> > parallel reduces the equivalent series inductance, and adding an RLC
> > filter to the output makes the transition a lot cleaner.
>
> > The output as before is I(C5). =A0The simulation shows all sorts of
> > ripples at up to 12 GHz elsewhere in the circuit, which I really don't
> > think are real. =A0(The pHEMTs are that fast at 20 mA of drain current,
> > but surely not at 70 uA.)
>
> > Anyway, I think this can be made to work, assuming that the layout
> > person knows something about RF.
>
> And think about tricks like meander-back to reduce inductance.
>
> --
> Regards, Joerg
>
> http://www.analogconsultants.com/- Hide quoted text -
>
> - Show quoted text -

I had no problems.  You have to copy the *.sub file into the sub
folder and the *.lib file into the lib folder.

George H.

George Herold wrote:
> On Jun 2, 3:50 pm, Joerg <inva...@invalid.invalid> wrote:
>> Phil Hobbs wrote:
>>> Fred Abse wrote:
>>>> On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
>>>>>    OOPS! tried the LTC program and got the following errors:
>>>>> Questionable use of curly braces in "symattr spiceline rser=0.005
>>>>> lser={lcap}"
>>>>>      Error: undefined symbol in: "[lcap]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {rbi}"
>>>>>      Error: undefined symbol in: "[rbi]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Questionable use of curly braces in "symattr value {lbead}"
>>>>>      Error: undefined symbol in: "[lbead]"
>>>>> Questionable use of curly braces in "symattr spiceline rpar={rpbead}"
>>>>>      Error: undefined symbol in: "[rpbead]"
>>>>> Circuit: Version 4
>>>>> Fatal Error: Multiple instances of "Flag"
>>>>>    Maybe one of the problems was that all of the files were in a folder
>>>>> on another drive.
>>>> Ran first time for me.
>>> I posted a rebiased version that runs off +5V and gets the edge
>>> artifacts down to something reasonable.
>> I still get "Couldn't find symbol npnsub".
>>
>>  It uses single-ended drive for
>>
>>> the pHEMT differential pair Z2/Z3, in order to prevent capacitive gate
>>> current in Z3 from corrupting the output.  Using ten 39 pF caps in
>>> parallel reduces the equivalent series inductance, and adding an RLC
>>> filter to the output makes the transition a lot cleaner.
>>> The output as before is I(C5).  The simulation shows all sorts of
>>> ripples at up to 12 GHz elsewhere in the circuit, which I really don't
>>> think are real.  (The pHEMTs are that fast at 20 mA of drain current,
>>> but surely not at 70 uA.)
>>> Anyway, I think this can be made to work, assuming that the layout
>>> person knows something about RF.
>> And think about tricks like meander-back to reduce inductance.
>>
>> --
>> Regards, Joerg
>>
>> http://www.analogconsultants.com/- Hide quoted text -
>>
>> - Show quoted text -
> 
> I had no problems.  You have to copy the *.sub file into the sub
> folder and the *.lib file into the lib folder.
> 

Yes, I did that and then it worked. All you have to do is copy it into
the same directory where the *.asc file is. That's why I posted the
method to have it all inside the *.asc file, makes it much easier for
others to download and simulate.

-- 
Regards, Joerg

http://www.analogconsultants.com/

On Jun 2, 7:48=A0pm, Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net>
wrote:
> BillSlomanwrote:
>
> > On Jun 2, 6:16 pm, Fred Abse <excretatau...@invalid.invalid> wrote:
> > > On Fri, 01 Jun 2012 13:49:45 -0800, Robert Baer wrote:
> > > > =A0 =A0OOPS! tried the LTC program and got the following errors:
> > > > Questionable use of curly braces in "symattr spiceline rser=3D0.005
> > > > lser=3D{lcap}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lcap]"
> > > > Questionable use of curly braces in "symattr value {lbead}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> > > > Questionable use of curly braces in "symattr spiceline rpar=3D{rpbe=
ad}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> > > > Questionable use of curly braces in "symattr value {rbi}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rbi]"
> > > > Questionable use of curly braces in "symattr value {lbead}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> > > > Questionable use of curly braces in "symattr spiceline rpar=3D{rpbe=
ad}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> > > > Questionable use of curly braces in "symattr value {lbead}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> > > > Questionable use of curly braces in "symattr spiceline rpar=3D{rpbe=
ad}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> > > > Questionable use of curly braces in "symattr value {lbead}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> > > > Questionable use of curly braces in "symattr spiceline rpar=3D{rpbe=
ad}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> > > > Questionable use of curly braces in "symattr value {lbead}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[lbead]"
> > > > Questionable use of curly braces in "symattr spiceline rpar=3D{rpbe=
ad}"
> > > > =A0 =A0 =A0Error: undefined symbol in: "[rpbead]"
> > > > Circuit: Version 4
>
> > > > Fatal Error: Multiple instances of "Flag"
> > > > =A0 =A0Maybe one of the problems was that all of the files were in =
a folder
> > > > on another drive.
>
> > > Ran first time for me.
>
> > Lucky you. I just got a long string of error messages, suggesting that
> > whatever end-of-line symbol Phil uses in his longer Spice command
> > strings isn't recognised as such by my version of LTSpice.
>
> I took the .asc file and copied it directly to the web host using sftp.
> I suspect that your client mungs the line endings somehow.

I used Firefox to look at your website, and cut and pasted from there
into Notepad, which is the most innocuous of the Microsoft editors. I
use Notepad to open my own .asc files, and cut and paste from Notepad
into Firefox to transfer LTSpice .asc files into my postings here, and
that seems to work.

--
Bill Sloman, Nijmegen

Am 02.06.2012 23:03, schrieb Joerg:

> Take the 0402 side case but place the vias in the pads. Should get you
> under 0.2nH. Now place two of those, super-close to each other, run the
> signal trace down the middle of them (sideways), connect one on the left
> and one on the right. GND would then be vice versa, first right, then
> left. Now the loops are opposing and so are the parasitic magnetic
> fields, helping the cancel each other. Well, to some extent.
>
> There are also caps with four pads but not sure how low they'll get you
> down in inductance.
>
> You can also get 01005 size caps from Murata and if still not good
> enough parallel a few, then the parasitic inductance is miniscule. But
> you'll probably need lasered vias in order to have them in-pad, I don't
> think those can be drilled.
>
> Have the ground plane right underneath and use a very thin board so the
> via lengths are small. Because they niow become a significant
> contributor to the parasitic inductance.

I find those x2y capacitors quite convincing.

<http://www.digikey.de/product-detail/de/160X14X224MV4T/709-1331-1-ND/2327231> 
  (and 400 others)

They lead to a via placement that cancels some of the inductance.
I have bought samples, but had no time to really test them.

Gerhard

Gerhard Hoffmann wrote:
> Am 02.06.2012 23:03, schrieb Joerg:
> 
>> Take the 0402 side case but place the vias in the pads. Should get you
>> under 0.2nH. Now place two of those, super-close to each other, run the
>> signal trace down the middle of them (sideways), connect one on the left
>> and one on the right. GND would then be vice versa, first right, then
>> left. Now the loops are opposing and so are the parasitic magnetic
>> fields, helping the cancel each other. Well, to some extent.
>>
>> There are also caps with four pads but not sure how low they'll get you
>> down in inductance.
>>
>> You can also get 01005 size caps from Murata and if still not good
>> enough parallel a few, then the parasitic inductance is miniscule. But
>> you'll probably need lasered vias in order to have them in-pad, I don't
>> think those can be drilled.
>>
>> Have the ground plane right underneath and use a very thin board so the
>> via lengths are small. Because they niow become a significant
>> contributor to the parasitic inductance.
> 
> I find those x2y capacitors quite convincing.
> 
> <http://www.digikey.de/product-detail/de/160X14X224MV4T/709-1331-1-ND/2327231>
>  (and 400 others)
> 
> They lead to a via placement that cancels some of the inductance.
> I have bought samples, but had no time to really test them.
> 

Yeah, Phil needs to buy a bunch of this stuff and also get used to the
01005 SMT size if he has more such design jobs coming. You can't even
see those anymore. And absolutely positively no sneezing on the job :-)

-- 
Regards, Joerg

http://www.analogconsultants.com/

"Joerg" <invalid@invalid.invalid> wrote in message 
news:a31c0lFfhpU2@mid.individual.net...
> Gerhard Hoffmann wrote:
>> Am 02.06.2012 23:03, schrieb Joerg:
>>
>>> Take the 0402 side case but place the vias in the pads. Should get you
>>> under 0.2nH. Now place two of those, super-close to each other, run the
>>> signal trace down the middle of them (sideways), connect one on the left
>>> and one on the right. GND would then be vice versa, first right, then
>>> left. Now the loops are opposing and so are the parasitic magnetic
>>> fields, helping the cancel each other. Well, to some extent.
>>>
>>> There are also caps with four pads but not sure how low they'll get you
>>> down in inductance.
>>>
>>> You can also get 01005 size caps from Murata and if still not good
>>> enough parallel a few, then the parasitic inductance is miniscule. But
>>> you'll probably need lasered vias in order to have them in-pad, I don't
>>> think those can be drilled.
>>>
>>> Have the ground plane right underneath and use a very thin board so the
>>> via lengths are small. Because they niow become a significant
>>> contributor to the parasitic inductance.
>>
>> I find those x2y capacitors quite convincing.
>>
>> <http://www.digikey.de/product-detail/de/160X14X224MV4T/709-1331-1-ND/2327231>
>>  (and 400 others)
>>
>> They lead to a via placement that cancels some of the inductance.
>> I have bought samples, but had no time to really test them.
>>
>
> Yeah, Phil needs to buy a bunch of this stuff and also get used to the
> 01005 SMT size if he has more such design jobs coming. You can't even
> see those anymore. And absolutely positively no sneezing on the job :-)
>

You can't even breath with those.


tm