Search results

  1. A

    I How inversion layer shields electric field?

    This question is somewhat relating to electronics but I think it fits better with physics. The leccture here (slide 13) shows that the gate to body capacitance (Cgb) in linear region is 0. However, there is no explanation at all. I tried to find the explanation from the reference book and got...
  2. A

    A Fixed effective charge in flat band voltage

    I am having a hard time understanding flat band voltage in MOS capacitor. Please see the picture below about MOS capacitor. Q0 is a fixed effective charge at the surface between oxide and semiconductor and it is positive here. The voltage across the oxide caused by the fixed charge ψox =...
  3. A

    Why LC tank only oscillates at resonant frequency?

    I am wondering why LC tank only oscillates at resonant frequency not other frequencies? Is there a physics explanation for that?
  4. A

    Confusion about a point and a line

    A point has no dimension and a line, which has dimension, is made from points together. How does something without dimension create something with dimension? I can't really make any sense of it. Could you share your opinions?
  5. A

    Conditions for Laplace and its inverse transform to exist

    I usually see that Laplace transform is used a lot in circuit analysis. I am wondering why can we know for sure that the Laplace and its inverse transform always exists in these cases. Thank you.
  6. A

    Boost-Flyback converter

    I am reading about Boost-Flyback converter and this is a bit confusing. Could you explain the role of D1 and C1 here? The lecture says that "D1 and C1deliver to the output the energy stored in the transformer leakage inductance Ld." I can't understand what is meant here. And could you explain...
  7. A

    Shared contacted diffusion in layout

    I am confused about shared contacted diffusion in CMOS layout. Is it possible to use shared contacted diffusion for two nMOS transistors with different widths? BTW, two nMOS and pMOS transistors are never shared contacted diffusion, right?
  8. A

    Output states of a CMOS gate

    Please help me with the question in the picture about pull-up and pull-down networks.
  9. A

    Approximation formula proof

    Hi. Please help me prove the approximation formula below given in my book. This is not homework question. Thanks.
  10. A

    2:4 decoder solution confusion

    Hi. I am confused a bit about the solution for 2:4 decoder in the picture below. Please help me with the question in the figure. Thanks.
  11. A

    Hi, At present, I am learning about Switched-mode power supply and Lo

    Hi, At present, I am learning about Switched-mode power supply and Low drop out regulator using CMOS. Could anyone suggest some good books about this? The main problem here is "using CMOS". Thanks.
  12. A

    Signal flow graph for two-port network

    Hi, this is part of an application note entitled "Low-Noise Amplifier Stability Concept to Practical Considerations" from Maxim. Could you help me with the question in the picture? Thanks. Source: http://www.maximintegrated.com/app-notes/index.mvp/id/1849...
  13. A

    Does NFmin in cascode LNA depend on the negative feedback inductance?

    Hi, This is a cascode LNA. Please help me with the question in picture. Thank you.
  14. A

    Help explain the capacitance definition in Spice

    Hi, In Spice, the capacitance between two points x, y is defined as follows: Cxy = - dQx / dVy for x != y Cxx = dQx/dVx Could anyone help me explain why it is defined like that? I know that C = dQ/dV but the formula above seems strange to me. Is my understanding below correct? Cxy =...
  15. A

    Zin of a circuit with independent sources

    Hi, This is not a homework question. I need to calculate input impedance for a LNA and this is part of it. How do you calculate input impedance, Zin, for the circuit below? I tried by applying an input voltage, V1, and calculate Iin. Input impedance will be V1/Iin. However, the expression...
  16. A

    Does energy of the signal lose after going through the filter?

    Hi, This is not a homework, just a problem that I can't figure out. Please help. Assuming that I have a low pass filter with cutting frequency, fc and a signal with many different frequencies (with some below fc and some above fc) is applied to the input of the filter. As we know, the...
  17. A

    Help understanding about wavelength

    Hi, I want to ask one question about wavelength. Here is a picture defining wavelength. To get a sinusoidal wave in space, we have to use a sinusoidal voltage source at transmitter, right? I mean if there is a sinusoidal voltage source at the transmitter to create a sinusoidal wave in space.
  18. A

    Why can't energy change abruptly?

    Hi, I want to ask your help about energy. Why can't energy change abruptly? If energy E changes abruptly then power P = dE/dt = ∞. I would like to know why this is impossible? I know that energy has to be conserved and they can only change from one form to the other. But why this process...
  19. A

    Voltage across diode

    I am reading an old thread and because it is too old I can't post reply. Here is the link: https://www.physicsforums.com/showthread.php?t=449044 I want to ask about the bold part. In the case, what is the voltage across the diode pair, zero or voltage source (Vin) when it is in positive half?
  20. A

    Connect an ideal battery across two end of a superconductor?

    Hi, What will happen if I connect an ideal battery across two ends of a superconductor? Assume all contacts are ideal, lossless. Is the current infinitive?
  21. A

    What is the difference in mechanisms in which IB1 and IB2 are formed?

    Hi, Can anyone help me? What is the difference in mechanisms in which IB1 and IB2 are formed in the picture below? http://en.wikipedia.org/wiki/File:NPN_BJT_Basic_Operation_(Active).svg Thanks.
  22. A

    That's that rho of s

    Please help me. What does the Prof. Walter Lewin mean by this "that is that rho of s"? Here is the video: http://www.youtube.com/watch?v=rp1orH7OC1c&list=SP854AA255B15C574C&index=17#t=31m20
  23. A

    Please explain why z = cosθ + jsinθ in this video.

    Hi, Please explain why z = cosθ + jsinθ in this video at 41:13 http://www.youtube.com/watch?v=OvDePn41fPY&list=SP854AA255B15C574C&index=2#t=39m46
  24. A

    Proof about complex conjugate of a function

    Hi, I need to understand the proof about complex conjugate of a function. g(z) = g*(z*) I don't know what it it called in English and can't search for it. If anyone knows where can I get the proof, please let me know. Thanks for help.
  25. A

    Design ultralow power, narrow band ADC

    Hi, I want to design an ADC with these specifications: Fin = 20MHz BW= 20MHz ENOB > 4 Power consumption P < 1mW Could anyone suggest me some ADC for this kind? I have searched a lot in IEEE but there are only two ADC with SAR ADC and time-interleaved ADC. The ultralow power consumption...
  26. A

    Sketch Vin-Vout in MOS transistor

    Can you help me check my work and tell me what is the application of the circuit? Homework Statement Sketch Vout versus Vin as Vin varies from 0 to VDD. Identify important points. Homework Equations MOS transistor equations in triode and saturation modes. The Attempt at a Solution
  27. A

    Why we write W/L = 50/0.5 not W/L = 100?

    Hi, I want to ask a question. In MOS transistors, the sizes of transistors often are given in the form: W/L = 50/0.5 or W/L = 10/0.5 I think there are implies behind the writing. If not why they don't just write W/L = 100 or W/L = 20 And can you explain the difference between the two: W/L...
  28. A

    Why the light increases when Prof. Lewin touch the end of the tube?

    Hi, Can you explain why the light increases when Prof. Lewin touch the end of the tube with his finger? He explained it but I am not quite understand it. The video is here at 45:40 : http://www.youtube.com/watch?v=ldJhMDuOGxY
  29. A

    Understanding Electricity and Circuits

    Hi, Can anyone take a look at this article and tell me your opinion? I want to know if this is true or not before learning it? http://science.uniserve.edu.au/school/curric/stage6/phys/stw2002/sefton.pdf
  30. A

    Can anyone tell me how the hole will move after this?

    Here is a set of pictures showing the ways electrons and hole move under electric field. Can anyone tell me how the hole will move after this? I mean that where the hole will move after the final image.
Top