Forward drop of diode vs forward drop of LED
$begingroup$
It is always said that forward voltage drop in the diode is around 0.7 volts. LED also being a diode, why does it have a greater forward voltage drop of around 3 Volts?
What is the model of LED that explains this higher voltage drop?
diodes photodiode
edited 1 hour ago
JRE
21.3k43769
asked 1 hour ago
VKJVKJ
358
$endgroup$
add a comment |
$begingroup$
It is always said that forward voltage drop in the diode is around 0.7 volts. LED also being a diode, why does it have a greater forward voltage drop of around 3 Volts?
What is the model of LED that explains this higher voltage drop?
diodes photodiode
edited 1 hour ago
JRE
21.3k43769
asked 1 hour ago
VKJVKJ
358
$endgroup$
1
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
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You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
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Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
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@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago
add a comment |
$begingroup$
It is always said that forward voltage drop in the diode is around 0.7 volts. LED also being a diode, why does it have a greater forward voltage drop of around 3 Volts?
What is the model of LED that explains this higher voltage drop?
diodes photodiode
edited 1 hour ago
JRE
21.3k43769
asked 1 hour ago
VKJVKJ
358
$endgroup$
It is always said that forward voltage drop in the diode is around 0.7 volts. LED also being a diode, why does it have a greater forward voltage drop of around 3 Volts?
What is the model of LED that explains this higher voltage drop?
diodes photodiode
diodes photodiode
edited 1 hour ago
JRE
21.3k43769
asked 1 hour ago
VKJVKJ
358
edited 1 hour ago
JRE
21.3k43769
asked 1 hour ago
VKJVKJ
358
edited 1 hour ago
JRE
21.3k43769
edited 1 hour ago
JRE
21.3k43769
edited 1 hour ago
JRE
21.3k43769
21.3k43769
asked 1 hour ago
VKJVKJ
358
asked 1 hour ago
VKJVKJ
358
asked 1 hour ago
VKJVKJ
358
358
1
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
$begingroup$
You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
$begingroup$
Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
$begingroup$
@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago
add a comment |
1
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
$begingroup$
You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
$begingroup$
Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
$begingroup$
@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago
1
1
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
$begingroup$
You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
$begingroup$
You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
$begingroup$
Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
$begingroup$
Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
$begingroup$
@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Different semiconductor junctions have different forward voltages (and reverse leakage currents, and reverse breakdown voltages, etc.) The forward drop of a typical small-signal silicon diode is around 0.7 volts. Same thing only germanium, around 0.3V. The forward drop of a PIN (p-type, intrinsic, n-type) power diode like a 1N4004 is more like a volt or more. The forward drop of a typical 1A power Schottkey is something like 0.3V at low currents, higher for their design working currents.
Band gap has a lot to do with it -- germanium has a lower band gap than silicon, which has a lower band gap than GaAs or other LED materials. Silicon carbide has a higher band gap yet, and silicon carbide Schottkey diodes have forward drops of something like 2V (check my number on that).
Aside from band gap, the doping profile of the junction has a lot to do with it, too -- a Schottkey diode is an extreme example, but a PIN diode will generally have a higher forward drop (and reverse breakdown voltage) than a PN junction. LED forward drops range from about 1.5V for red LEDs to 3 for blue -- this makes sense because the LED mechanism is basically to generate one photon per electron, so the forward drop in volts has to be equal to or more than the energy of the emitted photons in electron-volts.
answered 1 hour ago
TimWescottTimWescott
4,1401312
$endgroup$
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
add a comment |
$begingroup$
The voltage drop across a forward biased junction depends on the choice of materials. A common PN silicon diode has a forward voltage of about 0.7V, but LEDs are made from different materials and so have different forward voltage drops.
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
$endgroup$
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
add a comment |
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2 Answers
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active
oldest
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2 Answers
2
active
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votes
$begingroup$
Different semiconductor junctions have different forward voltages (and reverse leakage currents, and reverse breakdown voltages, etc.) The forward drop of a typical small-signal silicon diode is around 0.7 volts. Same thing only germanium, around 0.3V. The forward drop of a PIN (p-type, intrinsic, n-type) power diode like a 1N4004 is more like a volt or more. The forward drop of a typical 1A power Schottkey is something like 0.3V at low currents, higher for their design working currents.
Band gap has a lot to do with it -- germanium has a lower band gap than silicon, which has a lower band gap than GaAs or other LED materials. Silicon carbide has a higher band gap yet, and silicon carbide Schottkey diodes have forward drops of something like 2V (check my number on that).
Aside from band gap, the doping profile of the junction has a lot to do with it, too -- a Schottkey diode is an extreme example, but a PIN diode will generally have a higher forward drop (and reverse breakdown voltage) than a PN junction. LED forward drops range from about 1.5V for red LEDs to 3 for blue -- this makes sense because the LED mechanism is basically to generate one photon per electron, so the forward drop in volts has to be equal to or more than the energy of the emitted photons in electron-volts.
answered 1 hour ago
TimWescottTimWescott
4,1401312
$endgroup$
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
add a comment |
$begingroup$
Different semiconductor junctions have different forward voltages (and reverse leakage currents, and reverse breakdown voltages, etc.) The forward drop of a typical small-signal silicon diode is around 0.7 volts. Same thing only germanium, around 0.3V. The forward drop of a PIN (p-type, intrinsic, n-type) power diode like a 1N4004 is more like a volt or more. The forward drop of a typical 1A power Schottkey is something like 0.3V at low currents, higher for their design working currents.
Band gap has a lot to do with it -- germanium has a lower band gap than silicon, which has a lower band gap than GaAs or other LED materials. Silicon carbide has a higher band gap yet, and silicon carbide Schottkey diodes have forward drops of something like 2V (check my number on that).
Aside from band gap, the doping profile of the junction has a lot to do with it, too -- a Schottkey diode is an extreme example, but a PIN diode will generally have a higher forward drop (and reverse breakdown voltage) than a PN junction. LED forward drops range from about 1.5V for red LEDs to 3 for blue -- this makes sense because the LED mechanism is basically to generate one photon per electron, so the forward drop in volts has to be equal to or more than the energy of the emitted photons in electron-volts.
answered 1 hour ago
TimWescottTimWescott
4,1401312
$endgroup$
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
add a comment |
$begingroup$
Different semiconductor junctions have different forward voltages (and reverse leakage currents, and reverse breakdown voltages, etc.) The forward drop of a typical small-signal silicon diode is around 0.7 volts. Same thing only germanium, around 0.3V. The forward drop of a PIN (p-type, intrinsic, n-type) power diode like a 1N4004 is more like a volt or more. The forward drop of a typical 1A power Schottkey is something like 0.3V at low currents, higher for their design working currents.
Band gap has a lot to do with it -- germanium has a lower band gap than silicon, which has a lower band gap than GaAs or other LED materials. Silicon carbide has a higher band gap yet, and silicon carbide Schottkey diodes have forward drops of something like 2V (check my number on that).
Aside from band gap, the doping profile of the junction has a lot to do with it, too -- a Schottkey diode is an extreme example, but a PIN diode will generally have a higher forward drop (and reverse breakdown voltage) than a PN junction. LED forward drops range from about 1.5V for red LEDs to 3 for blue -- this makes sense because the LED mechanism is basically to generate one photon per electron, so the forward drop in volts has to be equal to or more than the energy of the emitted photons in electron-volts.
answered 1 hour ago
TimWescottTimWescott
4,1401312
$endgroup$
Different semiconductor junctions have different forward voltages (and reverse leakage currents, and reverse breakdown voltages, etc.) The forward drop of a typical small-signal silicon diode is around 0.7 volts. Same thing only germanium, around 0.3V. The forward drop of a PIN (p-type, intrinsic, n-type) power diode like a 1N4004 is more like a volt or more. The forward drop of a typical 1A power Schottkey is something like 0.3V at low currents, higher for their design working currents.
Band gap has a lot to do with it -- germanium has a lower band gap than silicon, which has a lower band gap than GaAs or other LED materials. Silicon carbide has a higher band gap yet, and silicon carbide Schottkey diodes have forward drops of something like 2V (check my number on that).
Aside from band gap, the doping profile of the junction has a lot to do with it, too -- a Schottkey diode is an extreme example, but a PIN diode will generally have a higher forward drop (and reverse breakdown voltage) than a PN junction. LED forward drops range from about 1.5V for red LEDs to 3 for blue -- this makes sense because the LED mechanism is basically to generate one photon per electron, so the forward drop in volts has to be equal to or more than the energy of the emitted photons in electron-volts.
answered 1 hour ago
TimWescottTimWescott
4,1401312
answered 1 hour ago
TimWescottTimWescott
4,1401312
answered 1 hour ago
TimWescottTimWescott
4,1401312
answered 1 hour ago
TimWescottTimWescott
4,1401312
4,1401312
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
add a comment |
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
$begingroup$
Schottky is spelled Schottky.
$endgroup$
– J...
27 mins ago
add a comment |
$begingroup$
The voltage drop across a forward biased junction depends on the choice of materials. A common PN silicon diode has a forward voltage of about 0.7V, but LEDs are made from different materials and so have different forward voltage drops.
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
$endgroup$
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
add a comment |
$begingroup$
The voltage drop across a forward biased junction depends on the choice of materials. A common PN silicon diode has a forward voltage of about 0.7V, but LEDs are made from different materials and so have different forward voltage drops.
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
$endgroup$
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
add a comment |
$begingroup$
The voltage drop across a forward biased junction depends on the choice of materials. A common PN silicon diode has a forward voltage of about 0.7V, but LEDs are made from different materials and so have different forward voltage drops.
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
$endgroup$
The voltage drop across a forward biased junction depends on the choice of materials. A common PN silicon diode has a forward voltage of about 0.7V, but LEDs are made from different materials and so have different forward voltage drops.
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
answered 1 hour ago
Elliot AldersonElliot Alderson
6,01611018
6,01611018
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
add a comment |
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
$begingroup$
Choice of materials, and doping concentration. Material is a more significant effect, though.
$endgroup$
– Hearth
1 hour ago
add a comment |
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1
$begingroup$
This is one of those questions where the answer is to read a solid state physics book.
$endgroup$
– Matt Young
1 hour ago
$begingroup$
You know, I don't think I've seen this question asked on here before, but it seems like a fairly easy misunderstanding for beginners to get, which means it's a useful one to have on here. Good question!
$endgroup$
– Hearth
1 hour ago
$begingroup$
Some decent reading: ledsmagazine.com/articles/2004/01/what-is-an-led.html
$endgroup$
– Peter Smith
1 hour ago
$begingroup$
@Hearth. Thank you for your appreciation
$endgroup$
– VKJ
1 hour ago
$begingroup$
You might note that at room temperature the forward voltage of an LED can be 1.2V or so for an IR LED, 1.8V or so for a red LED or 3V or so for a white (really blue) LED. I have a datasheet here for a 245nm (UV) LED that has a typical Vf of 10V.
$endgroup$
– Spehro Pefhany
1 hour ago