Questions tagged [electronics]

Electronics is the study of electric circuits and electrical components, and the design of useful devices. Some questions in this tag may be more appropriate for the [Electrical Engineering(https://electronics.stackexchange.com/) SE site.

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17 views

Storing info -DVD vs CD [closed]

Why is it that a DVD stores 30 times as much information as a CD? Does it have anything to do with the wavelengths of the lasers used? If so, how?
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Can someone explain me the following line: “The RC circuit averages past history at the input with a weighting factor of e−Δt/RC.”

"The RC circuit averages past history at the input with a weighting factor of e−Δt/RC."
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Doubt about the impedance of the Instruments

It is correct to say that the instruments that measure signal have a large impedance as opposed to the instruments that generate signal, whose impedance turns out to be small. I know that this is true ...
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Fourier analysis for the study of signals doubt [closed]

I know that Fourier analysis in an experimental way is very important, but can we say that it is the most powerful tool we have to study signals? or what is it that most contributes to the study of ...
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Problem when simulating with Proteus [closed]

I am simulating circuits using Proteus software but I was wondering why I could in no way simulate the impredance of instruments such as a multimeter, an oscilloscope or a signal generator. I would ...
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1answer
23 views

When a capacitor discharges in a simple RC circuit, is it treated as an active component?

While deriving expression for the voltage across capacitor in a discharging RC circuit, I stumbled across whether I should treat the capacitor as an active or a passive component(To properly apply the ...
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26 views

Which device we can use in place of relay for 35000 volt? [closed]

What can we use in place of relay for very high voltage and current supply switching (let's say 35000 volt).
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48 views

Why is n-p-n transistor typically “faster” than p-n-p transistor?

I know that the n-p-n transistor is faster than p-n-p transistor. My book explains it with 'the hole is faster than an electron. But I think the hole is empty space of electron, so these speeds should ...
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How does forward biasing of both junctions in BJT leads to saturation?

As far as I know, for an NPN-BJT, when both (base-emitter and base-collector) are forward biased; we consider the operation to be in saturation mode. Here, the transistor functions as a short circuit ...
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Is Collector current depends on width of base and Vcb in forward active mode? (common base transistor)

I asked this question on electronics.SE but I don't get any good answer may be because its more of a physics question . I just started reading about transistors from book "Microelectronics ...
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Effective density of states $N_c$ at different temperature for $\rm Si$

For Silicon at room temperature, Nc = 2.8x10^19 per unit volume. For 300K, m*/m = 1.81 for Silicon. Now Nc is proportional to 1.5th power of both temperature and m* (effective mass). So, at any other ...
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Why don't we use an intrinsic semi conductor as a collector in an npn BJT device?

I was watching a video lecture which talked about how the doping level is varied across the Collector and the various reasons behind doing this. There was also the question about why Intrinsic ...
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Modulation Index of an AM wave

I have been given a question as RMS value of an RF(Radio Frequency) voltage after amplitude modulation to a depth of $50$% by a sinusoidal voltage is $80$ Volts. Calculate the RMS value of modulated ...
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In a common base configuration with a pnp and VBC≈0, why does an output current IC flow when VEB < 0

Suppose a common base configuration of a standard pnp bipolar-transistor with the base grounded. The idea is to use the transistor as an ideal diode (as by the Shockley equation): $$ I_C = I_0 \left(e^...
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A proof for why the “minority charge carrier concentration along the x-axis in a pn junction isn't constant ” confuses the hell out of me

I've been following Behzad Razavi's Microelectronics book. Here is the particular excerpt from the book which is confusing An interesting question that arises here is: are the minority carrier ...
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Full wave rectifier forwarding state

I have a full bridge rectifier with Forward Voltage, per Element $1 \ \mathrm{V}$ at $8 \ \mathrm{A}$, does this mean that between $-1$ and $1 \ \mathrm{V}$ at input the bridge will not forward ...
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28 views

What could be the meaning of “illuminance” in this home device?

I bought a Xiaomi sensor that measures light intensity. The data I get from it is called illuminance_lux and the unit is supposed to be ...
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32 views

How to determine waveform of thermal (white) noise?

Here, the mean power of thermal noise is given by: $P = 4kT$ ($T$ = temperature, $k$ = Boltzmann’s constant) And the voltage in the instrument is, of course, thus given by: $V^2/R = 4kT$ The thermal ...
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45 views

Why is it hard to cool a mini-PC to room temperature?

I have this passively cooled mini-PC that froze every few days. After a lot of investigation I realized that it was overheating (running android studio and such) so I bought a fan, an arduino nano and ...
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Energy bands motion in an npn transistor

How do electrons move in an npn transistor along their energy bands, in active mode? How does the base current originate in this energy diagram?
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1answer
26 views

Why doesn't the extra electron in n type semiconductor due to doping by a pentavalent impurity create a hole?

Isn't the pentavalent impurity atom positively charged and attracting the electron? On receiving the energy why doesn't the electron create a hole in the valence band as it moves to the conduction ...
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What's the difference between amplitude and phase modulators in sideband generation?

As far as I know, both modulators (amplitude and phase modulators) can generate sidebands at the output spectrum. Are there any differences between these two modulators for the generation of sidebands ...
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2answers
75 views

How does current density depend on diameter of wire? [duplicate]

I understand Current density $J =n e v$ [$n=$ carrier concentration per unit volume, $e=$ charge on electron, $v=$ drift velocity] Which is independent of area of cross section of wire (and hence the ...
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Are resistors, inductors, capacitors the only possible passive components in this universe?

I wonder whether or not there is a possibility to find another passive component (with value either $X$ or $Y$) that will change the well known RLC circuit equation below $$ L\; \frac{\mathrm{d}^2 \; ...
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52 views

Physics vs Electronics (Smartphone charger)

Basically, an electric charger consists of a transformer, which transfers electrical energy from one inductance to another.. َAs i imagine the process physically the first circuit (inductance) should ...
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7answers
131 views

What's the point of using resistors?

When there is a battery connected in an open circuit, there is some induced e.m.f, right? Now, if a battery is connected across its ends with a wire, with no resistances or any other appliances, and ...
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Is the digital representation of acoustic waves directly proportional to displacement(or pressure)?

In most audio editing software(like audacity) waveform can be viewed. Zoomed in these look like actual waveforms. Out of curiosity I downloaded some frequency sweep test files(which are intended to ...
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51 views

Is the performance of electronic devices affected by their age? [closed]

I always wondered what happens inside an electronic component during its lifetime. I am aware that passive or active electronic devices can have their performance decreased over a long period of ...
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1answer
19 views

Position dependent $y$ channel reading in lock-in in a photocurrent microscope setup

I am currently building a scanning photocurrent measurement setup. It basically focuses a CW laser down to $50\ um$ size on the sample and scan the laser beam over the sample (a metal) and record the ...
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Does an electron of n side recombines only with holes of p side or also get recombined at the n side itself?

Suppose there is an electron at the n side.Does the electron have to travel until the p side to get recombined or is it like an electron travels some distance along n side gets recombined ,then ...
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26 views

Do electrons on $n$-side loses its energy to fall into holes on $p$-side during forward bias in a diode?

So in a diode in forward biased condition the electron from n side recombines with the hole in p side.I also understood that the electrons in n type are in conduction band and holes in p type are in ...
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23 views

With a half-wave rectifier, wouldn't the charges accumulated on one side?

In a normal alternating current circuit, the charges just travel back and forth, so they won't accumulate. However, if only half wave can pass through, then will the charges get accumulated on one end ...
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42 views

Current flow in potentiometers

In the following circuit involving a potentiometer; Assume $V$ to be the voltage produced by the cell in the primary circuit across the length $AJ$ of the potentiometer wire, and $E$ to be that ...
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Linear Energy Transfer & Absorbed Dose

I started to learn about radiation effects in semiconductor devices and integrated circuits. I am trying to understand the physics of it. Have some questions. The first is if you could suggest a good ...
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1answer
27 views

In which household equipment can i find an alternator or a generator or a dynamo (about 17V)? [closed]

equipment required: dynamo or an alternator or generator (all should be small about 17V). As due to COVID19 i am unable to buy any of the mentioned equipment as the online shopping service providers ...
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1answer
33 views

How does RF communication between electronic circuit elements affect the circuit?

The other day, a friend and I were looking at a simple resistor-capacitor-inductor circuit. As we were looking at the circuit, he mentioned that the capacitors and inductors "talked" to each ...
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1answer
59 views

Heaters in parallel and series [closed]

I have a heater rated at 13 kW with two identical heating elements connected in parallel with a 240VAC power supply. If I connect elements in series instead what should be my expectation: That the ...
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19 views

A problem with high pass filter circuit

What physically happens when the input frequency is "too high"? At "normal" frequencies the circuit should act as expected and block lower frequencies while getting only higher ones. I found that if ...
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20 views

What is the flat band voltage?

I do not understand what the flat band is. I am studying the MOS structure and the teacher told us that the flat band voltage is the voltage that we have to apply to the MOS so that the effect of the ...
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15 views

Why a semiconductor exhibiting negative differential resistance is inherently unstable?

A semiconductor exhibiting negative differential resistance is inherently unstable. Why is that? Why a random fluctuation of carrier density at any point in semiconductor produces a momentary space ...
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Can someone explain why electrons of n type(conduction band,higher energy),fall into holes in p type(valence band,lower energy) during forward bias?

As I was learning semiconductor physics I learned that holes are deficiency of electrons.I also learned that the electrons from the n type material combine with the holes in p type and the electrons ...
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12 views

Can you apply horizontal shift to obtain the absorption spectra for III-V ternary and quaternary compounds

For a multi-junction (MJ) solar cell application, can you apply a horizontal shift to obtain the absorption spectra when you don't have the available data? For example, if you know the absorption ...
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1answer
52 views

Intrinsic carrier concentration and bandgap

My understanding is that the intrinsic carrier concentration of a wide bandgap material tends to be lower than that of a narrow bandgap material. $$ n_i = \left(N_cN_v\right)^{1/2}e^{\left(\frac{-E_g}...
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3answers
53 views

If voltage causes current to flow how can a battery have constant voltage but supply different amounts of current?

The question arises from the fact the voltage provided across battery terminals is constant no matter how much current is drawn (for non-ideal batteries the current draw is limited but still can be ...
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1answer
51 views

Does the shifting of the Fermi energy level of an intrinsic semiconductor mean that $n \neq p$?

It has been stressed out in the books that I've consulted that, for an intrinsic semiconductor, $n=p$. However, with this in mind, they also derivate the following equation: $$E_{F_i}=\frac{E_c+E_v}{...
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1answer
35 views

Magnetic analogy to the transistor?

Is it physically possible to substantially change a large magnetic field with a smaller one analogous to the electric field at the gate being able to partially or completely block the flow from source ...
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18 views

BJT phototransistor operation

I was wondering if I have understood the working principle of the BJT phototransistor. When light is absorbed by electrons in the emitter, enough electrons are energetic enough to cross the depletion ...
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3answers
55 views

By what mechanism does a solar flare overload electronics?

I apologize for my ignorance, but I lack the underlying knowledge to meaningfully research this myself. My knowledge of both Solar Flares and EMPs comes almost exclusively from pop-sci reading. I've ...
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1answer
87 views

How Equilibrium is Reached and Voltage Shared in a Series Circuit with Two Resistors [closed]

I've been reading up on basic electronics recently and to help me understand things better, I've been writing down my understanding of what I've read in layman's terms. One thing I've struggled with ...
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2answers
34 views

Why is the sum of currents in a diode constant?

Why is the sum of currents in a diode constant? Please answer my question I'm very appreciated

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