All Questions
Tagged with semiconductor-physics electric-circuits
122
questions
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How can red LEDs still give a faint glow at a voltage of only 1.4V? [duplicate]
How can a red LED work at a voltage of only $1.4{\rm V}$? Red photons have an energy of $1.77{\rm V}$ if we use $\lambda = 0.7\mu\text{m}$ in the relation:
$$ E = \hbar \omega = \frac{2\pi\hbar c}{\...
- 4,913
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1
answer
60
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Can a DC voltage excite a pure semiconductor (or insulator) from the valence band to the conduction band?
I have a question I am sticking around and can't find a satisfying answer. Say I have an intrinsic semidonductor at zero Kelvin (no electrons in conduction band). I apply a DC voltage across it. Can ...
- 21
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1
answer
49
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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 ...
- 229
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1
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38
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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) ...
- 107
2
votes
1
answer
62
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How can an electric current flow between the end of the channel and drain?
In my book, it explains why current can flow even if the channel ends:
The device still conducts: as illustrated in figure, once the electrons reach the end of the channel, they experience the high ...
- 107
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1
answer
50
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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-...
- 107
-2
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1
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68
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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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1
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69
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Diode confusion
Consider the following diagram
Here, the diode is in forward bias, and allows current to flow. However, I am slightly confused why this is the case. A diode is defined to only allow current to flow ...
-1
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2
answers
179
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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 (...
4
votes
4
answers
764
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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 ...
- 442
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1
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71
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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 ...
- 11
2
votes
2
answers
92
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Does KVL don't hold in pn junction reverse bias?
Does KVL hold in pn junction reverse bias because any reference about semiconductor physics provide that figure
if we apply KVL around the loop won't be zero it will be equal to $V_{bi}$
then how KVL ...
- 597
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1
answer
195
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Drift current and diffusion current in depletion region of diode at equilibrium
The diffusion current for a diode at the edge of the depletion region is $I_D=I_S(e^{qV_A/VT}-1)$. Under an unbiased condition$(V_A=0)$ at equilibrium, $I_D$ will be $0$. The drift current should be ...
- 135
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1
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58
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Current Amplification in Common Base Transistor
How does a common base transistor amplify current if a small part of its emitter current gets divided into base current and the rest goes to collector current? If the input signal is applied to the ...
5
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2
answers
302
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How can modern transistors have width of only a few dozen atoms?
We typically analyze transistor's work based on a work of a simple pn-junction diode, with some modifications if needed, as it is basically a particular configuration of pn-junctions. We assume the ...
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