Searching for ultra low Cjo diodes

P

Paul

Guest
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Thanks,
Paul
 
Paul <energymover@gmail.com> writes:

Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.
Click to expand...
Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.

--

John Devereux
 
On Wed, 20 Aug 2008 21:55:18 +0100, John Devereux
<jdREMOVE@THISdevereux.me.uk> wrote:

Paul <energymover@gmail.com> writes:

Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.
Click to expand...
The smallest commercial chip diode I've seen is 0.02 or maybe 0.03 pF.
The smallest packaged one I know of is around 0.2 pF.

John
 
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> writes:

On Wed, 20 Aug 2008 21:55:18 +0100, John Devereux
jdREMOVE@THISdevereux.me.uk> wrote:

Paul <energymover@gmail.com> writes:

Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.

The smallest commercial chip diode I've seen is 0.02 or maybe 0.03 pF.
The smallest packaged one I know of is around 0.2 pF.
Click to expand...
So he just has to put 20 in series? :)


--

John Devereux
 
On Aug 20, 1:30 pm, Paul <energymo...@gmail.com> wrote:
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Thanks,
Paul
Click to expand...

The diodes will be used for ultra low power, so it doesn't matter to
me how small the junction area is.

Paul
 
On Aug 20, 1:55 pm, John Devereux <jdREM...@THISdevereux.me.uk> wrote:
Paul <energymo...@gmail.com> writes:
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.
Click to expand...

I would like small caps. Makes for a nice stressful day under the
microscope. :)

Paul
 
On Aug 20, 2:24 pm, Paul <energymo...@gmail.com> wrote:
On Aug 20, 1:55 pm, John Devereux <jdREM...@THISdevereux.me.uk> wrote:

Paul <energymo...@gmail.com> writes:
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.

I would like small caps. Makes for a nice stressful day under the
microscope. :)

Paul
Click to expand...


The Skyworks Inc. DMK2790-000 GaAs Schottky diode has a device
capacitance of 0.055pF. It says Cj0 is 0.05pF and average Ct is ~
0.063pF.

http://origin-products.skyworksinc.com/landingpage.jsp?familyname=GaAsFlipChip&Role=Public&ShowCatalog=H&Selector=false

Although I don't see any buy button for this diode. I think it's
expensive.

Paul
 
On Aug 20, 1:55 pm, John Devereux <jdREM...@THISdevereux.me.uk> wrote:
Paul <energymo...@gmail.com> writes:
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.

--

John Devereux
Click to expand...
I did a quick hack estimate of capacitance between a couple of 20mil
square pads 40 mils apart on 1/16 inch FR-4, in this way: the
capacitance per inch of a differential microstrip with 20 mil traces
separated by 40 mils is 2.4pF/inch (more or less). So .02 inches of
that would be about .05pF. I would expect fringing fields to add a
bit to that. Putting a package on top of those pads makes things
worse, as does having wires that come from the pads and end up very
close together at their ends. Guess you could shrink the pads
further, though you still end up with wires that come pretty close.

I wonder why the need for such low capacitance...

Cheers,
Tom
 
On Aug 20, 3:16 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Wed, 20 Aug 2008 21:55:18 +0100, John Devereux

jdREM...@THISdevereux.me.uk> wrote:
Paul <energymo...@gmail.com> writes:

Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Are there are *any* discrete components with capacitance that small?
The capacitance between its mounting pads would likely be more than
that.

The smallest commercial chip diode I've seen is 0.02 or maybe 0.03 pF.
Click to expand...

May I ask what diode chip part number is and manufacture? I may be
interested in purchasing a few hundred bucks worth initially if they
are reasonably priced per diode.

Thanks,
Paul
 
On Aug 20, 4:30 pm, Paul <energymo...@gmail.com> wrote:
Hi,

Does anyone know of inexpensive (less than 30 cents each @ QTY 1000)
high frequency Schottky diodes with no more than 0.01pF per diode?

The best I can come up with are from Skyworks Inc., which are around
0.1pF, although they have some that are a bit less capacitance, but
they're expensive.

Thanks,
Paul
Click to expand...
Check out the MDT Corporation MP61000 series of PIN diodes:
http://www.mdtcorp.com/prodfiles/MDT%20GaAs%20PIN%20diode.pdf
Also, I have used the gate-source junction of RF junction FETS as low
capacitance diodes. You also get the benefit of low leakage.
 
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