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  1. J

    Magnitude and direction of k vector

    I didnt understand the question. The magnitude is 2(pie)/wavelength. I get 78500 rad/cm which is pretty wrong as guess. Where would angle come into picture? Ref: https://www.millersville.edu/physics/experiments/062/index.php Shouldn't direction be like i + j + k ? So will it be like: |k|cos30...
  2. J

    How is this graph Hamiltonian and Eulerian?

    Is the graph Hamilton and Eulerian? The website says the graph is Hamilton and Eulerian but I think it's wrong. Ref: https://scanftree.com/Graph-Theory/Eulerian-and-Hamiltonian-Graphs There is no path that covers all paths only once. Any help? I think the graph is drawn wrongly.
  3. J

    (resolved) Seebeck effect: why can't electron+hole combine at cold end?

    Hi, In seebeck effect: Ref: Once the red region is hot, the electrons and holes move toward cooler region i.e. bottom. So there is a positive potential toward right side of cold side and negative region toward left side of cold side. So why can't the electrons and holes combine here only...
  4. J

    Wireless Power Transfer (is this correct)

    Ref: https://www.semanticscholar.org/paper/Design-and-Simulation-of-Different-Wireless-Power-Baroi-Isla m/dc19ecfde904964704777ab5adef96d5d6846f1f I couldn't find the working of this circuit so I guess it would be like: Initially transistor is OFF, so the current flows through Base, and...
  5. J

    How does a PLL work?

    From reference: https://www.elprocus.com/phase-locked-loop-operating-principle-and-applications/ It says that the PD produces an output that is DC level proportional to (Fi - Fo) (I think it has typo. It should be '-' but they've printed '+'). Then the low pass filter removes the high...
  6. J

    Royer Oscillator Working Principle

    Hi, I am studying Wireless Energy Transfer and I find Royer Oscillator in that. Ref: Wikipedia https://en.wikipedia.org/wiki/Royer_oscillator I am unable to understand how it works. I found a diagram here: Ref: https://www.smps.us/inverters.html It says that (quoted from webstie): In practice...
  7. J

    How does this have 24 transistors?

    Our professor is teaching this circuit and she mentioned there are 24 transistors. But I counted and it comes out to be 22 T1 to T4 needs 2 (transistor) * 4 = 8 transistors Each inverter needs 2 transistors. so 7 inverters need 14 transistors. total 22 transistors. Unless we're also creating a...
  8. J

    Engineering Output waveform after input rising edge and before output falling edge

    A is given waveform, we have to use circuits to get B and C waveform. For B we can use an And Gate with 2 inputs, X and Y. X is buffered (to get some delay) and is fed to Y input of And Gate. So we'll get waveform B. But I don't know how to get C waveform. The question is that even if I extend...
  9. J

    Diode Energy Band Diagram

    Ref: http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/pnjun2.html Hyperphysics Asstr Why does the band diagram shift up or down when I apply potential? Why does it shift down when positive potential is applied? Professor said it's because electron has negative charge and so we consider...
  10. J

    Oscillator Frequency of a Ring Oscillator with RC feedback

    I'm not sure how will this oscillator work. Assume A is low, so B will be high and the capacitor will charge through B-C- 2Mohm. Now even D has gone high, so A will be high and B will be low and C will discharge. I'm not sure how the voltage divider rule across RC will take into effect. I found...
  11. J

    D Latch using Transmission Gates

    My book has this diagram: Book: Digital Integrated Circuits by Jan M. Rabaey I don't understand the purpose of using the three Inverters. It's not mentioned in the book, nor could I find anything on the internet.
  12. J

    Engineering Longest Path in a Combinational Circuit

    First for logic-1 at output: So I get that for Logic 1, the OR-2 Gate must have one input has logic-1. Case1: Upper OR-Input is 1 of second OR Gate. So the longest path is Inv-1, Or-1, Or-2. Delay is 9ns. Case2: For lower input to be 1, the 'And-2' output has to be 1, and for that Or-1 output...
  13. J

    Frequency divider using CMOS

    I made a table using excel as: D is output. Like this I get Output frequency is same as input frequency. But I'm not sure if this is correct. PS: I'm aware I'm posting many questions, but I got interview exams coming up in August. Companies are gonna come to university for recruitment and thus...
  14. J

    Voltage divider rule for CMOS in 0-state and leakage current

    I use the voltage divider rule as output voltage = Voltage across R1 = 5 * ( 0.5 / (0.5 + 20) ) This comes as 0.122 V I'm not sure why they've mentioned I leakage and does 0-state have any impact on answer.
  15. J

    Voltage Swing for NMOS

    Ref: Digital Integrated Circuits by Jan M. Rabaey I have trouble understanding two things: 1) Why will x charge to Vdd - Vtn1 and why not Vdd? 2) If x in left charges to Vdd - Vtn1, then in right also it would charge to Vdd - Vtn1... so Vy would charge to Vdd - Vtn1 - Vtn2... so why have they...
  16. J

    Engineering Input and Output Impedance of an Opamp Circuit

    I know for ideal opamp the input Z is infinite, and output Z is 0, but not sure about this opamp.
  17. J

    Engineering Voltage across the output resistor for this opamp circuit

    Here is question: Find voltage across R3 options: 10V 11V 5V 2V Attempt: No current flows through Opamp, so 1mA flows through R3, this gives voltage across R3 = 1ma * 1K = 1V. But that is not in option. Where am I wrong? No current flows inside or outside opamp, right?
  18. J

    Why does PPG (photoplethysmography) Use Infrared and Green Both Light

    Hi Everyone, I'm doing research in Implanted Devices in Human Body (Sensors, Hearing Aid, Pacemaker) for my college course. I've started with FitBit that uses the PPG Principle. But I'm struggling to understand why the FitBit uses both Green and IR LED whereas the sensor at the receiving end is...
  19. J

    Channel length modulation in a MOSFET

    Hi, I'm struggling to understand how channel length modulation takes place in mosfet. The books n internet said that as drain side is positive, there is less potential difference between positive gate and positive drain, while there is more potential difference between positive gate and zero...
  20. J

    A For MOSCAP: why is surface potential constant after Vg = Vth

    Hi, I'm studying MOSCAP at university and there are 3 regions based on Vg. Accumulation Depletion Inversion For P substrate the surface potential increases as I increase the gate voltage (positive). The books say that at Vg = threshold voltage the surface potential is maximum. But why does it...
  21. J

    A How is the inversion Channel formed in SOI Mosfet?

    Hi, I'm studying MOSFET in detail and I'm struggling to understand how the channel is formed in case of SOI Mosfet. For normal mosfet A positive Gate to source voltage attracts electrons from P substrate towards Gate and thus a channel is formed. But in case of SOI There is a buried Oxide...
  22. J

    A 2-d and 3-d model for contact resistance of M/n-Si (book?)

    Hi, We're studying Contact resistance and the professor has given assignments on contact resistance. But I cant find any books to refer to. Here is one sample question: The books I'm referring to are ones by Donald Neaman, SMZ, Kanos. but none of them have any mention of 1-d or 2-d model for...
  23. J

    A Why does Efm shift in Mosfets

    Hi, I'm studying MOSFET and the book says that when N-channel mosfet has negative or positive gate voltage, the energy band diagram will shift. I don't understand why Efm shifts. Now when Vg is negative the Efm shifts upwards, Why? And when later when Vf is positive the Efm also shifts again? I...
  24. J

    Engineering Rate of change of current in an R-L Circuit

    Homework Statement Homework Equations Current cannot change suddenly through inductor unless input is impulse voltage source. The Attempt at a Solution since input is DC source we have i(0+) = i(0-) so we have di/dt at t = 0+ is 0. Is it correct? Book has mentioned answer as B which is weird...
  25. J

    Continuous or differentiable

    Homework Statement Homework Equations Solve using limits. Function is continuous if it's graph is continous throughout. here the (x-1) term gets cancelled in numerator and denominator. So we have a continuous graph of (x+1). The Attempt at a Solution The (x-1) term gets cancelled from...
  26. J

    Reference to this formula X = cube root of R

    Hi, Sorry for this weird question. My computer crashed and also the notes in it. I had a book wherein I'd written all the formulae. There is one formula in notes of Power System. X = cube root of R. I remember there was a website that even had its derivation, but I don't have the bookmarks...
  27. J

    Probability that more girls than boys go on the field trip

    Homework Statement Homework Equations First use equations to find out number of boys n number of girls. Then use probability concepts. The Attempt at a Solution Number of boys + number of girls = 12 Boys = Girls + 2 So we get Boys = 7, girls = 5. Select more girls than boys in a group of 3...
  28. J

    Output of transfer function given impulse response and input the

    Homework Statement Homework Equations Find laplace of x(t) and h(t) Multiply the laplaced values to get Y(s) Find inverse laplace to get y(t) The Attempt at a Solution In book the circled term isn't there. Why does that go away? Book gets y(t) as In laplace why does the e5t term go away?
  29. J

    Fourier transform (got right answer, but not matching graph)

    Homework Statement Homework Equations Scaling property and property of dual. I got the answer. The Attempt at a Solution I got the answer using scaling property and using property of dual. x1(t)---> X2(W)----(another fourier transform)--->2(3.14) x1(-w) But I think the final answer should be...
  30. J

    Ripple frequency of three phase half bridge converter

    Homework Statement Homework Equations Three phase half controlled bridge rectifier can have 3 pules at output or 6 pulses depending on firing angle. The Attempt at a Solution Ripple frequency is m times the input frequency where m is number of pulses. It can be 3 or 6. So why have they...
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