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How to measure p-n junction diode junction capacitance?
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SeanB:

--- Quote from: German_EE on May 22, 2016, 07:29:09 pm ---The article here describes the use of LEDs as varicaps, maybe not so useful for your application but the measurement technique is interesting:

http://www.hanssummers.com/varicap/varicapled.html

--- End quote ---

I guess if you redo the tests using 1W leds you will get higher capacitance, just because of the much larger physical die in the package. Reverse voltage will be a limit though, along with leakage current.
danadak:
1) You really don't know what the p-p voltage on the junction will be. That's pretty critical in this case.

2) Since there *is* resistance associated with the equivalent circuit, you very much need to know how this impacts your oscillator.  It's the good old R in series with C is a different C than C in parallel with R for the same net impedance at a frequency fun and games.

This pretty much indicates in rev bias model is pretty much just C.

https://inst.eecs.berkeley.edu/~ee105/sp04/handouts/lectures/Lecture20.pdf

For sure this is not a simple design. As far as P-P Vjunc that is under user control, agc and circuit parameter scaling come
to mind in any linear oscillator. Varactor tuned oscillators pretty well understood. Of course the "normal" diode is not targeted
for varactor performance, but measurement principles the same. One has to do a model/error analysis to see what can be achieved.

It was just a suggestion.

I think the diode in controlled reverse bias in a phase shift network maybe one of the easier ways to do the measurement.
Maybe there are some agilent/hp notes on how their semi analyzers do semiconductor measurements. They are the masters
at this craft.

https://arxiv.org/ftp/arxiv/papers/1011/1011.3463.pdf

http://www.tek.com/sites/tek.com/files/media/document/resources/C-V%20Fundamental019%29%20020409.pdf


Regards, Dana.
uncle_bob:

--- Quote from: danadak on May 22, 2016, 11:02:07 pm ---1) You really don't know what the p-p voltage on the junction will be. That's pretty critical in this case.

2) Since there *is* resistance associated with the equivalent circuit, you very much need to know how this impacts your oscillator.  It's the good old R in series with C is a different C than C in parallel with R for the same net impedance at a frequency fun and games.

This pretty much indicates in rev bias model is pretty much just C.

https://inst.eecs.berkeley.edu/~ee105/sp04/handouts/lectures/Lecture20.pdf

For sure this is not a simple design. As far as P-P Vjunc that is under user control, agc and circuit parameter scaling come
to mind in any linear oscillator. Varactor tuned oscillators pretty well understood. Of course the "normal" diode is not targeted
for varactor performance, but measurement principles the same. One has to do a model/error analysis to see what can be achieved.

It was just a suggestion.

I think the diode in controlled reverse bias in a phase shift network maybe one of the easier ways to do the measurement.
Maybe there are some agilent/hp notes on how their semi analyzers do semiconductor measurements. They are the masters
at this craft.

https://arxiv.org/ftp/arxiv/papers/1011/1011.3463.pdf

http://www.tek.com/sites/tek.com/files/media/document/resources/C-V%20Fundamental019%29%20020409.pdf


Regards, Dana.

--- End quote ---

Hi

Except that there seems to be a desire from the OP to do it both forward and reverse biased.....

Bob
danadak:
Asleep at the switch, thanks for pointing that out.

Looks like ap notes discussing small signal C-V approach are the way to go.

In this the conductance is calculated as an approximation of the simple I-V curve
slope -

http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-012-microelectronic-devices-and-circuits-spring-2009/recitations/MIT6_012S09_rec16.pdf

Interesting enough that would simply lower Q in a resonant tank. Maybe not a big deal
in an oscillator approach ? Out of my league.....

Of course that does not handle the Cj problem in the measurement.


Regards, Dana.
sohail anwar:
What is PN Junction (Diode):
A PN Junction Diode is a two-terminal semiconductor device. It’s made up from a small piece of semiconductor material (usually Silicon), it allows the electric current to flow in one direction while opposes the current in other direction. In the Forward Bias, the diode allows the current to flow in uni-direction. On the other hand, when the diode is reverse biased it opposes the electric current to flow. A PN Junction Diode is a semiconductor device with two opposite region such as (P-type region and N-type region).

The P-region is called as the anode and is connected to a positive terminal of a battery and it has Holes in majority carrier and electrons in minority carrier.
The N-region is called as the cathode and is connected to the negative terminal of a battery and it has Electrons as a Majority carrier while holes as Minority carrier.
When the P-type semiconductor material is joined with the N-type semiconductor material, a P-N Junction is formed, hence resulting P-N Junction is also called as a P-N Junction Diode.

Source: http://www.studentsheart.com/pn-junction-diode/
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