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Diodes and their application

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Agent 009

New Member
Although considered old in the technology domain, diodes still have important and interesting applications nowadays. I just want to regroup their global uses in this chat...
 

Exo

Active Member
:?: What do you mean... You want us to give examples of what diodes are used for?
 

Ravi

Member
The European system for classifying semiconductor diodes involves an alphanumeric code which employs either two letters and three figures (general purpose diodes) or three letters and two figures (special purpose diodes). The first two letters have the following significance:

1st letter-semiconductor material

A germanium
B silicon
C gallium arsenide etc
D photodiodes etc

2nd letter-application

A general purpose
B tuning (varicap) diode
E tunnel diode
P photocoltaic diode
Q light emitting diode
T controlled rectifier
X varactor diode
Y power rectifier
Z zener diode

In the case of diodes for specialised application, the 3rd letter does not generally have any particular significance. Zener diodes have an additional letter (which appera after the numbers) which denotes the tolerance of the zener voltage. The following letters are used:

A plus or minus 1%
B " " 2%
C " " 5%
D " " 10%

Zener diodes also have additional characters which indicate the zener voltage.
 

Wuey

New Member
Can someone please explain some of the following specs of an LED:

nm = 90
PdW = 45nW
if mA = 15
if mA(peak) = 50
Min = 1.7
Vf(V). Typ = 2.1
Max = 2.8
IV Min = 3.0

Thanks.
 

Agent 009

New Member
Reply to All

Hi everyone. I'm gonna reply to all of the posts.
Exo: I'm a second-year student majoring in computer engineering, so I may not - and certainly cannot - give all examples about use of diodes. As a matter of fact, I wanted to get examples, not to give ones.
Someone Electro:I think you know that diodes let current pass in both ways. And I'm not so new to electronics. Just trying to blend in the electronic world.
Ravi:Well... Thanks a lot! I really appreciate this type of reply, the informative one. I'm seeking communication with the electronic community, and I wish anybody who knows a bit to join me.
Wuey:I'll do my searches and I'll reply to you...

Thank anyway for all those who posted...
 

Agent 009

New Member
To Wuey

For your question, here's what i got:
-Pd: Power Dissipation, in mW
-If: Continuous Forward Current, in mA
-Ifm: Peak Forward Current 1, in mA
-Vf: Forward Voltage
Now, any parameter followed by min shows the minimum value for operation, typ for typical, and max for maximum
 

Agent 009

New Member
Application 1

For the first example of diodes' uses I'd like to discuss, is the ESD Protection system, used in applications like GPS (Global positioning System), and other... If anybody knows a little about this system... Well, you're welcome to tell us...
 

Optikon

New Member
Well, I do not think that GPS systems have anything to do with using diodes as ESD protection..I'm not sure if you are looking to discuss something particular about GPS or just diode applications for ESD.

Monolithic diodes are typically used for overvoltage protection and usually need to be of a low leakage type and of course they need to have a fast response but they are not designed for prolonged exposure to the over volt conditions and sometimes external current limit resistors are needed.

On the other hand, there does exist components designed specifically for ESD protection like TVS diodes and varistor devices. These types of devices use different materials to accomplish the fast resonse and power handling capability (ruggedness to repetetive over-volt conditions)
 

Agent 009

New Member
Well, while searching for zener diodes, I found an article on the ESD protection. I don't have an idea about the ESD Protection system, but the article stated that the application was widely used, specially in GPS. So I opened the subject seeking more knowledge about this system than giving information about it. If you know more about the ESD protection, and are sure that it doesn't have anything to do with diodes, well the article I read could be faulty, or I just misunderstood it... Anyway, your knowledge is appreciated if shared...
 

Noggin

Member
One way to use diodes for ESD protection is by placing diodes inside of microchips from input pins to Vdd. Since a normal silicon junction diode is mainly some n-type and p-type material, and when you're building a microchip (be it a simple 'or' gate or a more complex microprocessor) you're largly laying down fields of doped silicon among others.

If you want to place a diode between a pin and Vdd, then just plop down the two fields. When the techs make your chip, it'll have internal diodes for protection. I assume a similar process is done from gnd to the IO pins. This protection of course is not foolproof....

I also assume that these diodes why chips are always rated on the inputs being just a bit below ground, and a bit above Vdd. If you went too far below ground or above Vdd, the diodes would open up (forget the correct term) and allow the current to pass through to the pins, hopefully safely.

If the article was written by someone who was not familiar with ESD protection on microchips and they talked to someone about a particular chip which just so happened to be a GPS then it is very possible they misudnerstood and thought this form of protection was ONLY used for GPS application. But I am NOT saying that this is the case.

As for the comment about diodes letting current flow one way that you addressed, an ideal diode allows current to flow one way excluding zeners (and maybe some others.) Actually, a zener might not be classified as an ideal diode, so making the claim about an ideal diode may actually be valid.
 

Noggin

Member
Agent 009 said:
Well, while searching for zener diodes, I found an article on the ESD protection. I don't have an idea about the ESD Protection system, but the article stated that the application was widely used, specially in GPS. So I opened the subject seeking more knowledge about this system than giving information about it. If you know more about the ESD protection, and are sure that it doesn't have anything to do with diodes, well the article I read could be faulty, or I just misunderstood it... Anyway, your knowledge is appreciated if shared...
As far as zeners in ESD....

zeners have a reverse breakdown voltage much like most other diodes have a forward voltage. By placing a 5.1v zener in a circuit, you can latch a line to keep it from going above 5v or too far below 0v such as in the circuit below.
 

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Agent 009

New Member
I think you used Orcad PSpice to do that, no? the 9th edition maybe... It's not that I don't know ANYTHING about diodes, but I wanted to know the relationship b/w them and the ESD protection system, which, I repeat, I don't have an idea about it...
 

StopGo

New Member
Uses of Diodes - heres a few I can think of.

Bridge rectifiers
Voltage level shifting (e.g. 5V to 3.3V logic)
Thermal compensation in transistor circuits.
ESD protection (as mentioned)
Light emiting diodes.
Crystal set (AM demodulation)
Charge pumps (DC - DC converters)
Inductive load snubbing.
Zener diode voltage regulators.
Battery protection diode.

Theres plenty more obscure applications.. can anyone else think of more simple uses for the humble P-N junction ?
 

Styx

Active Member
dont forget logic
Good-old DIODE-OR and DIODE-AND
 
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