How do these LEDs work?
I bought some LEDs that they can show you 2 colors.
They don't have 3 bases but when I change the polarity, they will show me another color!
I know that Diodes can be run only in one direction,
but why those LEDs don't obey this rule?
Answer:
They have 2 diodes inside the glass/plastic encapsulation. The idea came from ESD protection structure, where the double diodes are placed flip and flop, so they will take turns on the ON and OFF depending on the polarity.
As for the colors, LEDs are made of compound semiconductors (III-V). Re-visit your periodic table of elements from your chemistry class. Different combination of these elements will give you different colors. For example:
AlGaAs (Aluminum Gallium Arsenide) : red
AlGaP (Aluminum Gallium Phosphide) : green
GaN (Gallium Nitride) : blue or white
etc. etc. etc...
There is more than one LED in the package...
Ron.
Circuit is a parallel circuit, one LED faces one way, the other is an parallel facing the other way. They are both contained in the same package
Think about the name : Light Emitting Diode. The light emitting part is still a diode.
they just made two diodes in one. one LED is opposite of the other, just like in TVS (sort of). And i know most biColor LED do have 3 legs for a common cathode.
As my idea probably it is two diodes with two kind semiconductor that the kathode of first is connected to the other diode's anode.And the first anode is connected to the other diode's kathode.Then at every bias voltage one of the diodes is on and the other diode is off.Then at every voltage(+/- and sufficient magnitude neither big nor small) one of the diodes propagates the light.The diode package is one.
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They don't have 3 bases but when I change the polarity, they will show me another color!
I know that Diodes can be run only in one direction,
but why those LEDs don't obey this rule?
Answer:
They have 2 diodes inside the glass/plastic encapsulation. The idea came from ESD protection structure, where the double diodes are placed flip and flop, so they will take turns on the ON and OFF depending on the polarity.
As for the colors, LEDs are made of compound semiconductors (III-V). Re-visit your periodic table of elements from your chemistry class. Different combination of these elements will give you different colors. For example:
AlGaAs (Aluminum Gallium Arsenide) : red
AlGaP (Aluminum Gallium Phosphide) : green
GaN (Gallium Nitride) : blue or white
etc. etc. etc...
There is more than one LED in the package...
Ron.
Circuit is a parallel circuit, one LED faces one way, the other is an parallel facing the other way. They are both contained in the same package
Think about the name : Light Emitting Diode. The light emitting part is still a diode.
they just made two diodes in one. one LED is opposite of the other, just like in TVS (sort of). And i know most biColor LED do have 3 legs for a common cathode.
As my idea probably it is two diodes with two kind semiconductor that the kathode of first is connected to the other diode's anode.And the first anode is connected to the other diode's kathode.Then at every bias voltage one of the diodes is on and the other diode is off.Then at every voltage(+/- and sufficient magnitude neither big nor small) one of the diodes propagates the light.The diode package is one.
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