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lowest leakage, lowest Vf diode?

I need a diode which leaks less than 100nA at 13V Vr from 25C to 50C,
and whose foward voltage drop is less than 400mV at 100mA, any ideas?
 
J

John Larkin

Jan 1, 1970
0
I need a diode which leaks less than 100nA at 13V Vr from 25C to 50C,
and whose foward voltage drop is less than 400mV at 100mA, any ideas?

I'd guess impossible. You'd need a schottky for the forward drop, but
they leak a lot. You might be able to fake it with a small mosfet,
depending.

John
 
C

CW Northrop

Jan 1, 1970
0
I need a diode which leaks less than 100nA at 13V Vr from 25C to 50C,
and whose foward voltage drop is less than 400mV at 100mA, any ideas?

100nA
 
M

Mike Harrison

Jan 1, 1970
0
I need a diode which leaks less than 100nA at 13V Vr from 25C to 50C,
and whose foward voltage drop is less than 400mV at 100mA, any ideas?

Peltier cooled schottky?
 
L

legg

Jan 1, 1970
0
I'd guess impossible. You'd need a schottky for the forward drop, but
they leak a lot. You might be able to fake it with a small mosfet,
depending.

Trouble is with leakage - the importance of sub-microamp drain leakage
in mosfets not being specifiable.

RL
 
F

Fred Bartoli

Jan 1, 1970
0
[email protected] a écrit :
I need a diode which leaks less than 100nA at 13V Vr from 25C to 50C,
and whose foward voltage drop is less than 400mV at 100mA, any ideas?

You'll probably won't find one, but depending on what you're trying to
do you might come up with something to do the trick.

What is it for?
 
J

John Larkin

Jan 1, 1970
0
Trouble is with leakage - the importance of sub-microamp drain leakage
in mosfets not being specifiable.

RL

I've used some that were consistantly good. When what you want to do
is impossible with guaranteed specs, you may have to settle for
actuals. Many semi "max" parameters are set where they are just to
speed up testing, so can often be finessed if one is careful.

Anybody know typical Idss for a 2N7002? It's spec'd at 1 uA, but I
suspect it's a lot less. I guess I could test a few. Gate leakage is
spec'd in nA, but it should be spec'd in electrons per second.

John
 
R

Robert Baer

Jan 1, 1970
0
legg said:
Trouble is with leakage - the importance of sub-microamp drain leakage
in mosfets not being specifiable.

RL
Do you not mean "not in the datasheet"?
The nanoamp region is very achieveable.
Since the OP wanted a low Vf diode, the problem with FETS is that the
gate control is sensitive to temperature, so a fixed bias scheme for
enhancement *or* depletion mode FET is a bit iffy - especially in this
case where the gate control voltage is going to change only a few
hundred millivolts.
Now that temperature sensitivity can be compensated some with a
scheme similar to my first Codatron (TM) design; the patent for that has
been released into the public domain - so feel free to use as you see fit.
Be advised that there can be some mis-matching between FETS, so that
for this "low Vf" application, that can have a large effect on the total
operation if multiple composite devices are needed (read: volume
production greater than 1000 per day).
That can be mitigated to a degree by making it as IC, wafer testing
offset before breakout and use.
Shoot, one could even trim one of the FETs my having graded sizes for
cutting out small areas; and the bias offset can also be trimmed (refer
to the ALD110800 series).
 
R

Robert Baer

Jan 1, 1970
0
John said:
I've used some that were consistantly good. When what you want to do
is impossible with guaranteed specs, you may have to settle for
actuals. Many semi "max" parameters are set where they are just to
speed up testing, so can often be finessed if one is careful.

Anybody know typical Idss for a 2N7002? It's spec'd at 1 uA, but I
suspect it's a lot less. I guess I could test a few. Gate leakage is
spec'd in nA, but it should be spec'd in electrons per second.

John
Agree on the leakage spec; many devices are *at worst* orders of
magnitude better than datasheet spec.
 
J

John Larkin

Jan 1, 1970
0
Agree on the leakage spec; many devices are *at worst* orders of
magnitude better than datasheet spec.

Last week's problem (the one MassivePratt squirmed out of addressing)
was the opposite: nearly 200 uA of current coming out of the input of
a cmos TinyLogic chip while the input voltage was well within the
rails. We were impressed.

John
 
R

Rich Grise

Jan 1, 1970
0
spec'd in nA, but it should be spec'd in electrons per second.

OK, Mr. Smartyboots, how many amps is(are?) one electron per second?

Please show your work. ;-)

Thanks!
Rich
 
J

John Larkin

Jan 1, 1970
0
OK, Mr. Smartyboots, how many amps is(are?) one electron per second?

Please show your work. ;-)

Thanks!
Rich

1.602e-19. It wasn't any work at all.

John
 
P

Phil Hobbs

Jan 1, 1970
0
John said:
I'd guess impossible. You'd need a schottky for the forward drop, but
they leak a lot. You might be able to fake it with a small mosfet,
depending.

John

The mosfet sounds about right, but it'd have to be connected backwards
on account of the source-drain diode, as in Bob Pease's polarity
protection trick. Maybe the OP could use a lithium battery to get the
gate bias right. It ought to be possible to power a comparator off
wherever that 100 mA is coming from.

Cheers,

Phil Hobbs
 
T

Tim Williams

Jan 1, 1970
0
John Larkin said:
Anybody know typical Idss for a 2N7002? It's spec'd at 1 uA, but I
suspect it's a lot less. I guess I could test a few. Gate leakage is
spec'd in nA, but it should be spec'd in electrons per second.

That's a good point- I was playing with a an, um, I think it was BS171, a
few weeks ago, in the trudge through my parts bin for an analog switch (for
which I eventually settled on a 2SK30 or something).

After discovering it was in fact a MOSFET, I had it set up on the breadboard
as a source follower into a 4.7kohm resistor from +12V or so. I connected
the gate to a wire in air. While playing, I discovered that a plastic bag,
charged with a stroke over my hair, switched it from two feet away, with no
apparent drift in the potential (that is, the distance at which it
saturates). Not bad at all. Probably, the adhesive label on the bottom of
the protoboard has more leakage than that thing.

Tim
 
O

oopere

Jan 1, 1970
0
John said:
1.602e-19. It wasn't any work at all.

John

This makes an interesting shot noise then! One shot per second, exactly :)

Pere
 
J

John Larkin

Jan 1, 1970
0
This makes an interesting shot noise then! One shot per second, exactly :)

Pere

It is possible to produce electrical currents that have little or no
random shot noise, to literally dispense exactly one (or more!)
electrons a second, rigidly periodically. SETs (single electron
transistors) are one way to do this.

But I guess that one electron a second does have a lot of shot noise
in a 1 Hz bandwidth.

John
 
W

Winfield Hill

Jan 1, 1970
0
Fred said:
acannell asked,


You'll probably won't find one, but depending on what you're trying to
do you might come up with something to do the trick.

What is it for?

What's it for indeed! Some special circuit configuration may be
able to handle the problem. For example, two 1n5822 diodes in
series will drop about 450mV at 100mA, and the connection node
between the two diodes can be bypassed with a resistor to ground
for the purpose of diverting most of the leakage current of the first
diode with 13 volts across it. If the resistor is a low enough value
the voltage drop across it from the first diode's leakage will be low
enough to avoid creating much leakage across the second diode.
 
T

Tim Williams

Jan 1, 1970
0
John Larkin said:
It is possible to produce electrical currents that have little or no
random shot noise, to literally dispense exactly one (or more!)
electrons a second, rigidly periodically. SETs (single electron
transistors) are one way to do this.

(Single Ended Triodes? ;-) )

The gain on those things must be horrific. One electron admitted for -- how
much capacitance to switch it?

Tim
 
M

Mike Monett

Jan 1, 1970
0
(Single Ended Triodes? ;-))
The gain on those things must be horrific. One electron admitted
for how much capacitance to switch it?

A Radio Frequency Single Electron Transistor (RFSet) can have a
bandwidth greater than 100MHz and extreme sensitivity. It is
described as a fraction of the charge on an electron.

Here's one that runs at 700MHz with a sensitivity of 3.63 * 10-5
e/RootHz. They show how it is measured:

http://www.brl.ntt.co.jp/people/fujisawa/papers/APL00543.pdf

Schoelkopf has a bunch of papers on them:

http://www.eng.yale.edu/rslab/projects.html#RFSET

Here's one that operates at 1.7GHz with a sensitivity of 1.2 * 10-5
e/Roothertz. Fig. 1 shows a SEM photo of the device.

http://www.eng.yale.edu/rslab/papers/RFSETScience.pdf

Fig. 3 shows the time-domain response for a large (~5.5 electrons
peak-to-peak) signal, 10 kHz triangle-wave applied to the gate. The
SNR looks very good:

These things fascinate me. I want one. No clue what I'd do with it,
but it would be nice to have laying around just in case I found a
use for it:)

Regards,

Mike Monett
 
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