All Questions
Tagged with semiconductors diodes
136
questions
7
votes
5
answers
3k
views
Series connection of diode and resistor. Why is there a constant voltage across the diode?
So I know that a diode can be described using the Shockley equation and after a certain voltage, the diode current begins to increase rapidly. The nominal 0.7 volts. I also know that this voltage ...
- 81
0
votes
1
answer
66
views
What is a precise definiton of "cut-in" voltage as applied to diodes?
What is the "cut-in" voltage or knee voltage of a diode or transistor?
In a lot of books I read that the cut-in or knee voltage of a diode (or transistor) is when the diode starts conducting ...
- 1
3
votes
2
answers
144
views
Interpreting Diode-Module Datasheet (Voltage Drop)
I'm trying to interpret the datasheet of a Dual-Diode Module, specifically the MF200C12F2N. The internal Circuit Structure is given below:
The Forward Voltage is given as 2.3V without any further ...
- 33
0
votes
1
answer
61
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Clarification on Diode Recovery Times and Conduction State
I have a diode in my circuit with reverse voltage of 100 V and forward voltage of 2 V.
It experiences a reverse voltage of 100 V and immediately the voltage changes to 10 V in forward direction so it ...
0
votes
2
answers
232
views
Using tunnel diode to cancel out armature resistance
Can we use tunnel diodes to cancel out armature resistance?
A tunnel diode when it is in its negative differential region under DC shifted AC(AC with some DC offset) and if the Vp-p of the AC is very ...
0
votes
3
answers
188
views
Semiconductor theory
Why is there no resistor in the circuit when analyzing hole and electron currents according to semiconductor theory?
- 31
1
vote
1
answer
569
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Understanding the formula of the saturation current in a PN-junction diode
According to Wikipedia, the saturation current in a diode is given by the following formula:
$$I_S = qAn_i^2\left(\frac{1}{N_D}\sqrt{\frac{D_p}{\tau_p}} + \frac{1}{N_A}\sqrt{\frac{D_n}{\tau_n}}\right)$...
- 121
0
votes
1
answer
106
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Contribution of hole diffusion current and electron diffusion current in a pn junction
I have recently got to learn that the hole diffusion current and electron diffusion current both point towards the N side in a PN junction? And the diffusion current is hence towards the N side.
And ...
- 23
0
votes
1
answer
50
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Drift Current in PN Junction and Barrier Voltage
I am reading this book, but the idea presented by it is very unclear.
It quotes:
However, I am not entirely convinced with the reason it provides here, like why are the minority carriers that reach ...
- 23
3
votes
1
answer
101
views
Why is diffusion current due to p side in a diode inversely proportional to doping concentration of p side in the case of forward bias?
In a diode at equilibrium, there are Pn holes on the n side of the junction. These are maintained by the dynamic equilibrium of diffusion due to holes = drift due to holes. When a forward bias is ...
0
votes
1
answer
145
views
Why doesn't a diode pass current when reverse biased?
If one tacks a P-type semiconductor to an N-type semiconductor, a P-N junction forms in which electrons diffuse from the N-type to the P-type causing a diffusion current. Some time passes, and an ...
- 361
0
votes
1
answer
403
views
Fermi levels in PN-junction under forward bias are not constant throughout each side
This is, in a way, a follow-up to this question.
I see the following band diagram for a forward biased diode everywhere:
In the above picture, I marked a point with potential zero (where battery is ...
- 163
16
votes
5
answers
4k
views
Resistance depending on voltage - the chicken and the egg?
If I understand correctly:
The resistance of some circuit components (like diodes) depends on the voltage across them.
When two components are connected in series: \$\frac{V1}{V2} = \frac{R1}{R2}\$
...
- 181
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 ...
0
votes
1
answer
54
views
What does the interface between lead(s) and the silicon chip look like inside a semiconductor package?
For a leaded semiconductor, like a diode or a transistor, one of the leads is usually the same piece of metal as the copper pad/heat spreader on the back, which is also shorted to one of the junctions ...
- 749
0
votes
1
answer
65
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Why in the output characteristic graph of BJTs, within the saturation region, is the collector current positive?
It is known that in the saturation region of the BJTs the pn junction is reverse biased. The reason for being reversed biased could be explained as follow:
Vce=Vcb+Vbe
Therefore
Vcb=Vce-Vbe
We can see ...
- 91
2
votes
1
answer
786
views
What are wettable flanks in semiconductor packages?
What are wettable flanks? Is there any difference between packages with wettable flanks and other leadless packages?
Can we say the package given above has wettable flanks?
2
votes
1
answer
121
views
Why aren't the majority charge carriers attracted by terminals of a battery when the p n junction is reverse biased?
It is clear that when the junction is reverse biased, the free electrons from the n side can not pass the depletion layer and fill the holes in the p side. But why will the free electrons not move ...
- 91
0
votes
0
answers
57
views
Power dissipation vs. heat dissipation for transistors and diodes
Are these two concept the same or different for semiconductors? Some power MOSFETS have power ratings in the hundreds of watts, and that's way too high for heat loss.
I try to understand 'power ...
- 749
7
votes
5
answers
2k
views
Why can't a P-N junction diode be used as a voltage regulator or reference in forward bias?
Usually, a Zener or avalanche breakdown region for a suitably doped P-N junction is used for voltage regulation as a substantial variation in the current (due to minority carriers) requires a ...
- 189
0
votes
1
answer
256
views
Select zener for minimal thermal drift
The voltage of a Zener diode in the Zener breakdown region depends on temperature. Suppose we have 3 Zeners with the following specs:
3.3 V rated Zener voltage at 5 mA
5.1 V rated Zener voltage at 5 ...
- 491
0
votes
1
answer
2k
views
Current density in an ideal PN junction diode
I found that the current density is as above.
The first question is: the logic is that when there is no external voltage applied, the diffusion current cancels the drift current. But there are four ...
- 101
0
votes
1
answer
561
views
Magnitude of current
The current of a germanium diode at room temperature is 100 uA at a voltage of -1 V. Predict the magnitude of the current for voltages of 0.2 V and -0.2 V at room temperature. Repeat the prediction ...
- 37
1
vote
2
answers
228
views
Why can't electrons leave the N side and enter the P side in reverse bias?
Why can't electrons (excess electrons) of the N side of a semiconductor diode enter the P side via the battery in reverse bias mode of PN junction? like this:
- 125
2
votes
1
answer
166
views
Diodes made using separate p and n-type semiconductors
Can a diode be made by connecting, in series, separate n and p-type semiconductors?
Assume that all ends are attached to Ohmic contacts. I am hoping that this will prevent any discontinuities in the ...
1
vote
1
answer
144
views
Thyristor latching current and holding resistance
Is there a formula for calculating the latching current of a thyristor and the resistance of the thyristor after it forward conducts and I_gate becomes 0? I couldn't find anything online; the ...
- 111
1
vote
1
answer
110
views
Majority Charge carriers and electron holes
Suppose I have an extrinsic semiconductor made of silicon and doped with phosphorous. Now, phosphorous has one more electron than silicon. After replacing one silicon atom, and taking its place, the ...
0
votes
2
answers
133
views
Find the output voltage of a diode circuit with two batteries connected in parallel
When Vi<-2V, the D1 & D2 both will be turned on and both of them will be considered as short circuits. But how do I find the output voltage with two batteries connected in parallel like this? I'...
- 3
0
votes
1
answer
737
views
Electric field of Schottky diode
Reference: Device Electronics for Integrated Circuits 3rd Ed. Richard Muller
I am trying to understand how to calculate the maximum electric field. The answer given in the book is $$E_{max} = \frac{-q ...
- 447
0
votes
1
answer
208
views
Voltage fluctuation due to AC in a half wave rectifier
I think I get the broader idea of using a diode as a half wave rectifier, but I have a question:
Who provides the forward voltage or knee voltage to start the diode for rectification? I am assuming it ...
- 271
0
votes
3
answers
166
views
Do we operate diodes past their barrier or cut off voltage?
I think I get the idea of barrier or cut of voltage (e.g., 0.7 V for Si). So diodes start conducting after cut voltage. I have few questions for the cut off voltage
What happens if I increase the ...
- 271
0
votes
0
answers
115
views
MOSFET diode configuration expression for dynamic bias
I'm trying to think of an elegant way of analytically expressing the gate voltage as a function of time \$V_g(t)\$ (= \$V_d(t)\$) for the diode configured MOSFET below.
The sources VDD and V1 are ...
- 1
2
votes
0
answers
57
views
How does the stored charge gets decayed when going from forward bias to zero bias?
In a pn junction diode when forward biased, excess electrons and holes get stored in p and n regions respectively.
If we short the diode by connecting p,n terminals with a wire,
how do these stored ...
- 1,150
6
votes
1
answer
3k
views
What is exactly modeled by 'transit time' in SPICE diode model?
I'm trying to find a precise definition for the transit time parameter in SPICE diode model. What I think is the official documentation for standrad Berkeley SPICE diode model says the following
...
- 577
0
votes
2
answers
843
views
Relation between forward bias and current in a diode
I have seen the VI graph to depict the relationship between forward bias and current. (left graph) and I think I get it. I have also seen another graph (right graph) to depict the relation between ...
- 271
1
vote
2
answers
1k
views
How can a Zener diode maintain a constant voltage?
A Zener diode in reverse bias more than breakdown starts conducting. If you increase the reverse bias:
It conducts more i.e current in it increases
The voltage across it remains same
I think I get ...
- 271
4
votes
4
answers
889
views
GaN Vs SiC physic properties
Here is a table which shows the différence between GaN and SiC:
I have no knowledge about physics of components. I have just some bases. In the above table I do not see real difference between SiC ...
- 2,478
0
votes
3
answers
1k
views
Does the current change in a Zener diode if I we increase the voltage
Zener diodes work in reverse bias in the breakdown region. At breakdown voltage, high current flows. I get till here. I want to know what happens if I increase the voltage after breakdown. Is there an ...
- 271
1
vote
2
answers
411
views
Why is the N side thinner than the P side in a photodiode?
I have been reading that a photodiode is built by sandwiching a very thin N type semiconductor togther with a thicker P type. Why is that so?
- 271
0
votes
2
answers
88
views
diode circuit without a voltage source
Will there be any current in the given circuit? If current exists then why do they exist and what will be the forward and reverse current and voltage(across the diode)?
As a student of Physics I will ...
2
votes
1
answer
993
views
What is the exact meaning of 0.7V voltage drop in a forward-biased diode?
this question is partially (but not totally) discussed here:
Why do diodes have a voltage drop?
Does the power drop on a diode become entirely heat?
The conclusion is that, in a forward-biased diode ...
- 3,550
1
vote
2
answers
207
views
Zener Diodes: How are different voltage drops achieved
How do semiconductor makers make zener diodes with a fairly wide range of voltage drops? In particular I'm curious how they get small increments - 3.3V, 3.6V 3.9V, 4.2V, 4.8V etc as I thought the ...
- 720
0
votes
1
answer
190
views
Part Identification, Board says C32 but it looks nothing like a capacitor and has 6/9 marking on it
First, I understand that you have to remove the components to fault find but this is just something to play with.
It's an internal HDD SATA adapter to USB3 with additional 12VDC for 3.5" HDDS. It ...
- 106
1
vote
1
answer
219
views
Formula for efficiency of half wave rectifier
I came across this formula for rectification efficiency of half wave rectifier:
η= (40.6 *resistance of load resistor )/ (resistance of load resistor+ resistance of secondary of transformer + ...
0
votes
1
answer
98
views
Why can't current flow in this circuit?
Boylested says that during the positive voltage half cycle diode D2 is cut off.
But why can't there exist a current flowing through the outer loop via C1, the secondary of transformer coil, C2, and D2 ...
- 167
0
votes
3
answers
744
views
Explanation for drift current
My question is why the concept of drift current or movement of minority charges is necessary while the pn-junction is formed. So drift current was explained to me in more or less this way
As the ...
- 23
3
votes
3
answers
501
views
Inability to forward bias diode in a simple circuit
I am struggling with forward biasing a diode in the circuit in the attached.
All the wires are attached properly, as there is continuity. The diode drops only 0.400V with a 9 V battery connected, the ...
- 197
-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?
5
votes
2
answers
227
views
Current-voltage characteristics of silicon carbide luminescence
I am currently studying the textbook Light-Emitting Diodes (3rd Edition) by E. Fred Schubert. Chapter 1.2 Henry Round's demonstration of the first LED says the following:
The mechanism of light ...
- 1,281
0
votes
0
answers
80
views
Why will electrons move from hole to hole in the p type at forward bias, but not from hole to n type at reverse bias?
This question is about a diode with a p type and an n type. At the forward bias the electrons from the n type to the p type and from hole to hole in the p type. My questions are these:
At the forward ...
- 299