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Type: Posts; User: vivekroy

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  1. Replies
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    Closed: Re: Loadpull for Differential PA

    Look at the symbol of a balun very carefully and you will see what we mean.
  2. Closed: Re: question about Friis equation with very large antenna gain

    Exactly as FvM mentioned. If Pr/Pt > 1, then it would also mean lambda/4piD >1 ==> D<lambda/4pi
    But by definition, far field extends upto infinity. Therefore the above conjecture is incorrect.
  3. Closed: Re: Overdrive voltage relationship to the op-amp speed

    Also increasing current increases speed in another way. The current available during slewinv increases.
  4. Closed: Re: differential amplifier design using ngspice

    Why do you have 'dff' before endc?

    AFAIK, a control section in NGSpice starts with a .control keyword and ends with .endc

    Also, have you tried adding a .save all before the control section?
    ...
  5. Closed: Re: Closed loop gain of this fully-differential amplifier

    Yes.. If A0 is large (and is typically the case) then the 'x' term will be such that x<<1..
  6. Closed: Re: Overdrive voltage relationship to the op-amp speed

    Vgs-Vth is called the overdrive in many textbooks.. Vth is the minimum drive required and anything above that is "over"-drive. :D

    P.S. Even Wikipedia has an article on it:...
  7. Closed: Re: Overdrive voltage relationship to the op-amp speed

    GBW = gm/2piCl and it increases linearly with increasing overdrive only if you increase it by increasing the current and not changing the W/L. If you keep the current constant and then increase the...
  8. Closed: Re: -3db frequency of the op-amp open loop gain

    Slewing is the most important characteristic I think as well.

    Assume that there is a two stage amplifier with the dominant pole at the end of the first stage. Assume that the input difference is...
  9. Closed: Re: S parameter extraction for MOSFET internal parameters

    I think what the OP is trying to refer to is that he is using s-parameter analysis in Cadence Spectre. During sp analysis, it also gives you two port Y and Z parameters which can be used to get a...
  10. Closed: Re: -3db frequency of the op-amp open loop gain

    Yes, for open loop -3dB is an important point.
  11. Closed: Re: S parameter extraction for MOSFET internal parameters

    It was HiCUM. Gummel Poon is quite limited for its use in a PA.

    But I get what you are saying. I will check it in a CMOS process.
  12. Replies
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    Closed: Re: Loadpull for Differential PA

    I inferred that you are doing mmwave from your previous posts. If that is the case, that current source will eat away unnecessary voltage headroom. I read somewhere that people don't use the current...
  13. Closed: Re: -3db frequency of the op-amp open loop gain

    If you want to use your op-amp as a crude open loop comparator, your -3dB can play some role in the initial part of the output before slewing effects take over.
  14. Closed: Re: Parasitic capacitor extraction: huge value

    I don't think that value is unrealistic. For example, in PTM from ASU (http://ptm.asu.edu/modelcard/HP/22nm_HP.pm) I see similar values. But what you have printed is the model parameters (parameters...
  15. Closed: Re: S parameter extraction for MOSFET internal parameters

    400f and 96f are quite far apart. I have done similar measurements in bipolar transistors at 28GHz and 60GHz but it was never this far off.

    Refer to the paper, "Parameter extraction technique for...
  16. Closed: Re: How do you choose input power while doing loadpull?

    The pout for optimum load is the pout you would get if you connected the optimum load (from loadpull simulation) and put in the input power at which you did the loadpull.

    It is not necessary to...
  17. Closed: Re: How to calculate bandwidth for this circuit, including lower and higher cut off f

    But doesn't this look like a stacked power amplifier? Do we need to care about open loop stability of a power amplifier? If we can get rid of the feedforward impedance, then for passive terminations,...
  18. Closed: Re: Problem in plotting I/O waveform in Cadence

    Use the delay function to plot the delay between the two wave-forms and then do a Y vs Y plot.
    Alternatively you can save both your voltage/current/charge waveform and your delay waveform in csv...
  19. Replies
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    Closed: Re: Verilog-a code to latch analog voltages

    Here you go


    // VerilogA code

    `include "constants.vams"
    `include "disciplines.vams"

    module veriloga_latch(vin,vclk,vout_sampled);
    input vin,vclk;
  20. Replies
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    Closed: Re: Verilog-a code to latch analog voltages

    Look at page 113 of http://www.lumerink.com/docs/VerilogA.pdf

    Your exact solution is given!!
  21. Closed: Re: Problem in plotting I/O waveform in Cadence

    Connect a capacitor to your charge pump output. Make sure its large enough so that when the CP turn on, the voltage does not change too much.

    Start with two vpulse sources that have a phase...
  22. Closed: Re: In PA, if the bias is VDD then how can swing be 2*VDD with inductive load

    You have the explanation there.

    If you want more insight into such behavior, refer to "Pulse, Digital and Switching Waveform" by Millman and Taub.
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    Closed: Changing the 'VDD' and 'VSS' value in CppSim

    By default most digital blocks in CppSim have an output between -1 and 1. I want it to be between an user-defined fixed set of values, for eg. 0 and 1.8. Till now I have been using a multiplier...
  24. Closed: Re: Help on Ocean scripting: run one analysis and use that results in another

    I don't like using calcVal in global variables. I always prefer using it in local variables. (Make sure to disable the global variables by unchecking the box next to the respective global variable)
  25. Closed: Re: Help on Ocean scripting: run one analysis and use that results in another

    Yeah, it is not a calculator function.

    I think maybe the SKILL Language Reference Manual?

    Or maybe in the SKILL API Finder which can be invoked from the Virtuoso CIW Window.
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