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# Questions tagged [pn-junction]

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13 views

### Carrier concentration of pn junction in reverse bias

I'm trying to understand the effect of forward and reverse bias in the carrier concentration of a pn junction. I know that in equilibrium the first picture below holds. When we apply forward bias, the ...
24 views

### Short N region diode

A diode was manufactured by making an abrupt junction between a region of length $W_p$ having a concentration $Na = 10 ^ {18} cm^{-3}$ and a region $W_n$ with $Nd = 5.10 ^ {15} cm^{-3}$ of ...
36 views

### Diode lifetime VS junction temperature

I have one bridge rectifier operating at the constant junction temperature of ~72°C, (GBPC3510W datasheet), which is rising to ~80°C in some specific cases. I'm trying to find a kind of "aging curve" ...
87 views

### Total current current equation in P-N junction

So Okay I get why there is a negative sign in the equation for diffusion current of holes since the gradience is actually negative if we put our coordinate axis in the bottom left corner for example ...
60 views

### Given a diode circuit and some of its values, how do I find the temperature?

Let's say I am given the following circuit: along with $$dV_p/dT=0.139mV/K$$: Defining V1 the voltage above Diode D1 and V2 the voltage above diode D2 , we use the expression for the current of a ...
176 views

### Deviation from typical I-V characteristics of a diode in high frequency

Why the diode shows a loop in the I_V characteristics?(Diode part N4003, Frequency was 100k) My instructor told me something regrading the retardation of charge carriers but I couldn't understand/find ...
90 views

### How do LEDs stay on constantly?

In a LED (light emitting diode,) a forward bias allows electrons to fill the vacancies in the p-type region, recombining with holes to emit a certain frequency of light. After a set amount of ...
60 views

### Confusion regarding Common-Emitter configuration of a BJT

This is a picture of a Common-Emitter Configuration of an n-p-n BJT, taken from a book :- For the BJT to be in active mode, the Base-Emitter junction should be forward biased, and the Collector-Base ...
56 views

### Photodiodes: the “generation” mechanism behind photocurrent

Assume I use a photodiode under zero-bias (that is in photovoltaic mode). How/why can a current flow in this bias condition? As far as I have understood the working principle of photodiodes, when ...
33 views

### Calculating Nmax in loaded bipolar junction transistor inverter

I have tried various methods for calculating N max here, and some have resulted in negative answers while others have resulted in an answer of around 1. Is my method correct? Or am I missing ...
83 views

### P-N Diodes in series. Is my solution correct?

I have attempted to work out a solution on a short question relating to p-n diodes. Is my solution correct? The question (from a past paper) : From the question I understand that there are two ...
60 views

### Forward Bias PN Junction

The depletion region is formed at the junction due to diffusion which creates a thin width of negative ions on the p side and positive ions on the n side whose electric field restricts further ...
14 views

### Linearly graded and step graded PN Junction represent uniform or non-uniform doping?

Linearly graded and step graded PN Junction represent: a) Non-Uniform Doping , Uniform Doping b) Uniform Doping , Non-Uniform Doping c) Uniform Doping , Uniform Doping d) Non-Uniform Doping , ...
54 views

### What bias voltage is applied to a PIN photodiode when connected only to multimeter

If I take just a PIN photodiode (e.g. BPW34 FAS ) and connect a multimeter to its terminals to measure current, for example: expose the photodiode to the sunlight and read current of ~1 mA on the ...
48 views

### Barrier voltage and temperature of a PN junction

Why does the barrier voltage of a PN junction decrease by increasing temperature ? Please if possible , i want to understand the inner physics of what happens
109 views

### BJT Active mode - How does it work

I am finding it difficult to understand how exactly this works and would appreciate any help. From my understanding: The emitter base junction has to be in forward bias meaning that Vb is more ...
147 views

### Find cause of diode destruction from destroyed diode itself

Is it possible to find the cause of power diode destruction, ie. if it was destroyed through: reverse overvoltage spike (reverse breakdown and subsequent thermal destruction due to reverse ...
102 views

### Estimate temperature for silicon (p-n junction)

I need to estimate the temperature at which p-n junction made of silicon lose it rectifying characteristics. ($N_A=N_D=10^{15}\,cm^{-3}$) $E_G$ is independent of the temperature and are 1.12 eV ...
44 views

### Diodes when voltage is applied

Does the hole injection take place from p semiconductor to n semiconductor in a pn junction diode? Or it takes place only in the case of a transistor?
72 views

53 views

### Above the barrier voltage does a pn junction behave ohmically?

I understand that below the barrier voltage no current flows, and once the required voltage is met the current rises exponentially, in accordance with the ideal diode equation. However at voltages ...
1k views

### Why does the depletion region penetrate more into the lightly doped region in a pn junction?

I have read at several places if we take exact same cubes of p and and n doped semiconductor material and form a junction, the depletion region(blue colored region in my drawing) will be asymmetric ...
793 views

### Relation between junction and capacitance and reverse bias voltage [closed]

Can someone explain how junction capacitance in reverse bias voltage depends on the rate of change of external diode voltage(vD)? I tried to find the answer on google but was not successful.
780 views

### Diode voltage dependence on temperature

Question: In the circuit D1 is a large-area, high-current diode whose reverse leakage is independent of applied voltage, while D2 is a much smaller, lower-current diode for which n = 1. At an ambient ...
100 views

### Why two seperataly doped semiconductors cannot be joined to form a junction? [duplicate]

My textbook says that when a slab of P-type semiconductor and another slab of N-type semiconductor are joined, they cannot form a junction because no matter however smooth the surface is, there will ...
114 views

### Diode Circuits using expotential model

simulate this circuit – Schematic created using CircuitLab Hi, Question: In the following, a string of three diodes is used to provide a constant voltage of about 2.1 V. We want to calculate ...
373 views

### Diode Modelling

simulate this circuit – Schematic created using CircuitLab Hi, Question: In the following, a string of three diodes is used to provide a constant voltage of about 2.1 V. We want to calculate ...
679 views

### Drift current and reverse saturation current

I have a few questions whose answers I couldn't find. All questions are in respect to a pn junction diode. 1) Does diffusion flow of current (even minimal/negligible) occur at reverse bias? 2) If ...
3k views

### Dynamic resistance of a p-n junction diode

The slope of the graph between current and voltage in a p-n junction diode, under both forward bias and under reverse bias, varies a lot on varying the voltage. Hence, given the graph, how do we ...
471 views

### What happened to Depletion region when biasing is Off after applying reverse biasing?

I was studying Diodes and I came across the information that when the diode is reversed biased the depletion region is increased. Now the depletion region is composed of neutral atoms that are ...
101 views

### Diode breakdown

I read in the book, "Microelectronic Circuits" that the breakdown of a pn junction is not a destructive phenomenon given that the breakdown current is limited to a safe value by an external circuit. ...
34 views

### Thin p+ side in photodiode

The diagram of the photodiode is shown below. Why is the p+ layer very thin here? Could we have used a n+p configuration instead?
470 views

### Constant voltage-drop diode model?

I'm in the process of learning about diodes and I'm currently learning about diode models. I came across the model called the constant voltage-drop diode model. So, let's say the diode built-in ...
308 views

### When would I not want to replace a PN diode with a Schottky diode

When repairing or maintaining equipment, or even during design revisions, why would I, for electrical reasons (not interested in the potential financial aspects) not want to replace a PN junction with ...
106 views

### Why current is constant during storage phase in reverse recovery experiment?

This is a simple schematic of reverse recovery experiment. As you can see, there is a constant current phase in the curve known as storage phase. My question is, why current is constant during ...
93 views

### Do photons come out when electrons and holes recombine inside a forward biased diode?

When electrons fall to a lower level orbital they emit light/radiation at a particular frequency. Is that the case for recombination? My question came from this speech at the following part: https://...
589 views

### why maximum value at middle of pn junction is negative?

Why the slope of the electric field of N side of the junction is positive and p side is negative.Also, why can't be maximum value be positive i.e on the Positive axis of the Electric field?Please ...