# 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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### Capacitance of multiple overlapping metal layers

Consider a set of metal plates arranged in a similar fashion to the picture below: The capacitance between the layer labeled M5 and the layer labeled M4 can be calculated (ignoring fringe effects) as ...
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### Electric: Why does NCC keep finding 5 parts in the schematic and 6 in the mocmos? [migrated]

Here's my schematic: And here's my mocmos: The number of wires and ports is the same but for some reason the mocmos has one extra part: enter image description here When I click on the supposed ...
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### Question about class A amplifiers [migrated]

I am trying to understand the working principle of a simple class A amplifier. Below you can find a diagram of the inner components. I am struggling to understand why the gain $G$ is given by the ...
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### Is there any electronic devices that maintain charged state?

I want to know how to make electronic devices that are continuously charged to + or - state on which surface when voltage is applied to utilize the dielectric polarization property, or if there are ...
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I am very new to electronics and am a physics student working on an assignment. I have a very simple circuit set up in my bedroom: A power source of DC +0.7A and +5.0V with a single resistor of 100 ...
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### I don't really get transistors. How do they work exactly in the active region?

So in an NPN transistor, when the base-emitter is forward biased, and the base-collector is reversed biased, electrons from the emitter get to the base. That part I understand, electrons are the main ...
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### How can charge neutrality be maintained for a forward-biased PN junction?

When a PN junction is forward biased, majority electons diffuse into p region and majority holes diffuse into n region, if we impose quasi-neutrality, then we have that in the p and n regiosn the ...
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### Would a diode more ideal than Shockley diode equation violate the second law of thermodynamics?

The Shockley diode equation describes the behavior of all diodes extremely well. Semiconductor p-n diodes and Schottky diodes are described by the very same equation. Furthermore, it applies to light ...
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### Current due to Ambipolar transport of excess carrier in semiconductors

I am reading Neaman's textbook and I am confused by the ambipolar transport phenomenon. According to what I have understood, if excess carriers are injected somehow into a doped semiconductor piece, ...
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### Why is potential continuous at dielectric conjunction?

Lets take for an example, a spherical capacitor with two dielectrics. The Electric Field will then be given by $$\frac{Q}{4\pi\varepsilon_0\varepsilon_r r^{2}}$$ We know that then the electric field ...
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### Minority-carrier only injection into bulk semiconductor

If an n-type bulk semiconductor sample was injected from the side with holes. Such that holes are injected uniformly into a small region near the side surface of the sample. Does this excess minority ...
1 vote
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### How can one make a visible light bulb that works through cyclotron radiation?

I figure that I first start with a charged particle accelerator. Let's say we can make this from electromagnets arranged in a circular ring in the XY plane with a magnetic field $B$, perpendicular to ...
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### Potential difference in a ring

Basically in a circuit there is a cell with a positive and negative end, and current flows through it - electrons are pushed by negative electrode and attracted to the positive electrode. But if say a ...
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### Reverse current

I'm getting started with electronics and couldn't help but wonder about this. When the PN junction diode is reverse biased, P connected to the negative terminal and N connected to the positive ...
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### Mysterious sound from measurement setup in "zero measurement"

Once a colleague showed me a sound measurement setup in a reverberation room, meant to measure (unwanted) sound from magnetostriction in ferrite cores. There was a problem creating a true "zero&...
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### Pulse to sine with the same frequency

I have a pulse signal with frequency f(t) And i want to generate from it a sine signal with frequency f(t) (f(t) doesn't vary a lot in time) Is there a method to do it directly with a function ...
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### Force on charge carriers in a simple circuit

Is it true that in a simple circuit where a simple conducting wire is connected to a battery, the force on each charge carrier is same in magnitude ? If yes, then can you explain how? I know that if ...
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### Microwave oven efficiency and conservation of energy

Wikipedia says that microwave ovens can be around 50-64% efficient at converting electricity into microwaves. Where does the energy lost at this stage go? And how much of the energy that is ...
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### Resistance in series also slows current down so why is resistance connected in parallel in galvanometer ammeter and not in series?

When we convert a galvanometer into an ammeter we connect the resistance in parallel, the only reason we connect a resistance in parallel with galvanometer is so less current passes and the flow of ...
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### For intrinsic semiconductors, is the gap Energy equals $E_c-E_v$ or $E_c+E_v$?

So I have a problem with the intrinsic Fermi Level because by definition it is in the middle of the gap energy, and knowing that Eg=(Ec-Ev), we should have Ei=(Ec-Ev)/2. But when we follow the ...
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### How a switching mixer works in this example circuit?

I am reading about lock-in amplifiers and came across this example circuit of a mixer: You have one sinusoidal input signal $e_1$ with a phase $\phi_1$ and the local oscillator has a square-wave ...
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### Holes near the junction on the n-side can readily float up the hill irrespective of their energy when the p-n junction is at equilibirum. Why?

Why does it not depend on their energy?
1 vote
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### EM wave emission from earphone wires due to varying current signal

if we listen to some audio signal on a wired earphone, then does the wire of the earphone act as a transmitter antenna to emit the audio signal as radio waves even though its strength might be ...
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### Saturation region of common emitter BJT

About the saturation region of common emitter Bjt it's written that In saturation mode both of the "diodes" in the transistor are forward biased. That means V(BE) must be greater than 0, and ...
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### When forming an n channel in an N MOSFET, do the pn junctions of the drain-substrate and source-substrate parts disappear?

When forming an n channel in an N MOSFET,, do the pn junctions of the drain-substrate and source-substrate parts disappear? Here's what I expected: When gate voltage (higher than threshold voltage) ...
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### Is the direction of base current always constant in a BJT transistor?

Is the direction of base current always constant in a BJT transistor? Excluding the transistor breakdown state, is the direction of the base current always the same in the four modes: active mode, cut-...
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### Voltage across the diode?

Why the voltage across an ideal pn junction diode remains 0.7 volts, even when the applied voltage exceeds 0.7 volts? Shouldn't it be the applied voltage minus the 0.7 V?
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### If an atom loses electron, it becomes a cation; it does not form a hole. However, when electron is lost from a bond, it forms a hole and not a cation

If an atom loses an electron, it becomes a cation, and when an electron is lost from a bond, it forms a hole. This is what the professor told the class, but I am not able to find the reason for that ...
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### What can cause a spot above my WiFi router's antenna? [closed]

Lately a weird dark spot has appeared right above the antenna of my wifi router. It wasn't there before. I have tried to wipe it and it got a little bit brighter but I don't think it's dust. My guess ...
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### Effect of Coaxial Cable Length on Capacitive Discharge

Summary: If I have a Capacitive Discharge through a coaxial cable to some load, how does the length of the cable effect the current felt by the load? I believe that the schematic breakdown for this ...
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### How do changes in a video file during editing relate to voltage levels?

I’m trying to understand the relationship between video editing and voltage levels. For instance, if I trim the first 10 seconds of an MP4 video file or add an audio track, how are these changes ...
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### Can two laser diodes of the same type and wavelength, be synchronized to emit light in the same phase, while working in a CW mode.?

Can two laser diodes of the same type, power and wavelength, be synchronized to emit light with lightwaves in the same phase, while working in a continuous wave mode (CW) ?
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### Why we are using coupling capacitor in AC amplifier? [closed]

Why we are using coupling capacitor in AC amplifier?
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### Why my DC thick charging cable is slower than a thinner one? (having same power rating & adaptor)

Does that means thick wire cause more current loss than thinner one?
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### Angular Velocity measured by a UGV on a curved path is equivalent to Angular velocity of UGV on a straight path

Pre-Condition An FOG IMU is mounted on a high speed Autonomous Vehicle to track linear acceleration and angular velocity of the vehicle under dynamic conditions, Here FOG Z axis (accelerometer + ...
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### How do computers store sound waves just by sampling the amplitude of a wave and not the frequency?

All of this just doesn’t make sense though. I mean, doesn’t the amplitude represent the loudness and the frequency the pitch? Aren’t they completely independent from each other? Is the book just ...
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### Impact of photodiod's active area density on quantum efficiency?

The quantum efficiency is a factor, telling me the ratio between optical input and electrical output. So I wondered, how does the efficiency depend on the density of the photodiod's active area? I ...
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### Resistors in high frequency

My question is this: Can we use ordinary resistors like those we use in labs(1.2K ohm), in high frequency (like 4GHz)?
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### Working of transistor

For the operation of the transistor, the base-emitter junction is forward-biased and the Base collector junction is reversed-biased. Due to the concentration gradient, electrons from the N side (...
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### Help understanding why built in voltage in PN junction created?

I was reviewing basic semiconductor physics and need some help understanding where my logic is incorrect. For a basic PN junction, the process of forming the depletion region is described as follows: ...
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### In four probe experiment why the graph looks like in low temperature

I found a graph between the log of resistivity vs inverse of temperature like this So in region 2, why is the graph going down?
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### From the physics standpoint, how should I align a USB Internet stick relative to the nearest cell tower in order to have the best signal? [closed]

I use this USB Internet stick: (Huawei E3372h-153) To connect to the Internet, I simply insert a SIM card into this stick and then insert the stick into a USB port of my laptop. Based on my ...
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### Isn't heating insulator enough for sufficient electrons to escape valence band and conduct electricity?

Diamond has about 5.5eV of energy gap, So If I heat diamond it will get atleast 1J energy which is enough to excite about 10^18 electrons, But Diamond still not conduct electricity, Why?
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### Potential effects of magnets on a Police Taser?

I couldn't find any similar topics and was curious if anyone had thoughts on the following: Could a magnet (ceramic and/or neodymium etc.) have an adverse affect on a Police Taser, if held to the ...
728 views

### Load Lines and Characteristic Curves

While studying electronic circuits involving diodes, I came across the concept of characteristic curve, which relates the voltage drop in a diode with the current through it. However, I was also ...
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### Why do we still consider a doping concentration in undoped MOSFET devices?

I am studying cryogenic behaviour of MOSFET devices especially the evolution of threshold voltage with temperature. I mostly measure FinFET and FDSOI devices, all which have supposedly undoped channel....
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### About electricity flow through a diode

I have read answer of Vintage in 11 July 2011 on Krzysztof Lewko's question Why can electricity flow only in one direction through a diode? I appreciate very much this answer and i vote as "this ...
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1 vote
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### Carrier concentration on forward biased pn-junction

I understand that when a pn-junction is forward biased minority carriers accumulate and form an exponential charge concentration in relationship to the distance from the junction, as the figure below ...
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under thermal equilibrium the pn junction have a built-in field let say it's $E_{1}$ , if we make a reverse bias the external battery provide a permanent field $E_{2}$ , so the total field inside the ...
I know that the equation is $$V = (S_B-S_A)(T_2-T_1),$$ but surely this output voltage must be proportional to the surface area (and probably thickness) of the Peltier device. What is the formula that ...