All Questions
Tagged with semiconductors led
24
questions
3
votes
2
answers
197
views
LED limit to short pulse and high power
I’m studying the viability of a small footprint distance detector that relies on a LED, a photodetector and some lenses. It’s meant for a distance above 150m, where the light beam travel time is ...
- 1,399
0
votes
1
answer
71
views
Diodes in parallel reduce current compared to single measurement
I have a photonics integrated circuit with two quantum well diodes. (exact description below)
If I measure the IV curve for each individual diode I get pretty much the same curve for both. but if I ...
4
votes
2
answers
416
views
Why does touching LEDs' ground terminal light them dimly?
Today I was making a little circuit with an LED strip (3 LEDs in series) and I noticed a curious fact that I am not sure how to explain. I wasn't sure of the operating voltage of the LED strip, so I ...
- 162
1
vote
1
answer
340
views
How to calculate the total power of a LED using solid angle?
I have a LED with the max power of 130mW/sr and an opening angle of +-10° (so approx. around 20°). I conducted an experiment using this LED, the LED shines light to an un-doped silicon semiconductor ...
- 11
0
votes
1
answer
72
views
How to convert spontaneous emission into stimulated?
I have a semiconductor diode that has spontaneous emission (LED).
The question is what can I change in the fabrication of the diode to improve its performance such that the diode gains a stimulated ...
-1
votes
1
answer
199
views
What happens when an LED burns out? [duplicate]
When an LED is burned out, specifically which part is burned out?
Is it the semiconductor or the wires?
Can we use a burned out LED to generate electricity?
4
votes
1
answer
476
views
Cut-off frequency of a LED
I'm trying to solve this problem:
A GaAs LED is at \$ 300 K \$ when the current density is 1000 \$A/cm^2\$
. The width of the active region is \$ 1 µm \$. Assume that, for that current, we are in the ...
- 1,431
0
votes
2
answers
77
views
Mechanism of conversion of electrical energy to EM energy in LEDs
I've always been intrigued that electrical energy can just disappear out of a circuit 'into the aether' as RF.
Of course thinking about it, some energy 'vanishes' as EM radiation even in a filament ...
- 1,008
1
vote
1
answer
76
views
Differential emission of LED die under changing current?
This is going to be a bit too specialist for most people, but here goes...
Normally we treat LEDs as point sources. However, they are actually flat chips that emit light from the surface. I am ...
- 14k
2
votes
1
answer
95
views
Cover element on LED component
From time to time I come across a solution in which uses an LED as in below picture:
This particular component is placed inside the module located in car interior. Button backlight application.
The ...
- 983
0
votes
0
answers
167
views
Ordinary LED response to nanosecond pulses
Can anybody explain to me the output waveform generated on pins of an ordinary LED when it is exposed to very short light pulses?
I can clearly see that there is a precise difference in the length of ...
- 291
7
votes
1
answer
2k
views
Will a Schottky diode save my LEDs against reversed voltage?
Consider the following schematic:
simulate this circuit – Schematic created using CircuitLab
Main question:
1) I am accustomed to use Schottky diodes to protect my circuits against reverse ...
- 942
0
votes
2
answers
168
views
What happens to the semiconductor in an LED when it is given voltage that it cannot handle?
Let us suppose we have an LED with the allowed voltage range of 1.5V to 4.5V and we gave it somewhat 12V. Now we know that the LED will instantly stop forever. But I want to know what will happen to ...
2
votes
2
answers
187
views
Measuring junction temperature of LED tape?
My boss at work wants me to figure out a method of measuring the junction temperature of an LED that is part of a reel of tape. Unfortunately, there is no datasheet for the LED modules themselves, ...
3
votes
3
answers
1k
views
Do an LED’s free electrons ever run out?
I’m aware that LEDs are doped with impurities on each p-type and n-type material to increase the charge carriers of each semiconductor.
My curiosity now is, how does each side continue to have extra ...
- 635
0
votes
2
answers
988
views
Easiest way to create a constant 1V voltage drop [closed]
I need to find a small, cheap, easy way to get a 1V drop in a circuit. It needs to be such that below 1V it acts like an open switch, and above 1V the drop is a constant 1V. Basically an LED without (...
- 59
0
votes
3
answers
330
views
How can I calculate the current through an LED? [duplicate]
I am trying to find out if increasing current increases the brightness of an LED.
I'm pretty sure this is the case now that I have looked into semiconductor band theory physics and p-n junctions.
...
- 1
1
vote
1
answer
4k
views
What is leakage current in an LED?
Is 'carrier leakage from the active region' of an LED the same as 'reverse leakage current'? If they're different what are their respective physical origins?
- 113
7
votes
4
answers
583
views
Why are 'modern' high-efficiency LEDs easier to damage than 'old' LEDs?
I have a few 'old time' LEDs from the late 80s and early 90s. The red and green 5mm LEDs (amber was a rarity, blue was 'impossible' back then). Not being very smart, I used to test them with a 9V ...
- 4,088
3
votes
3
answers
1k
views
LED typical and forward voltages
So, I was going through the spec sheet of super bright 5mm orange LED, and it was listed that the forward voltage is between 1.8V and 2.5V. Below that there was a property listed as 'typical voltage' ...
- 187
0
votes
1
answer
164
views
Self Heating of LED
I am using Red LED connected to B2902A SMU which can display current Voltage curve only.But i need to find out what is the temperature(Self heating) and how to find it using I/V curve.So that i can ...
- 19
12
votes
3
answers
8k
views
Why does the intensity of light in LEDs not increase with current after a particular value?
I read in books that light intensity from an LED does not increase beyond a certain value of current.
The amount of light emitted depends on the combination of holes and electrons. If so, then as the ...
- 783
4
votes
4
answers
663
views
Do LED have an unproductive base power consumption like incandescent bulbs?
To generate light from an incandescent body, like a tungsten filament,
the body needs to be heated up to a temperature minimum needed to emmit light from that material.
Up to that minimum temperature,...
- 1,086
-1
votes
2
answers
101
views
Using a single inverter to turn a light off
I'm planning on adding two strips of LED lights to the edge of my headlight enclosure. This is obviously an aesthetic "mod" however I'd like it to be semi useful as well. I'd like to be able to wire ...
