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Type: Posts; User: frankrose

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  1. Replies
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    Closed: Re: LDO & BUck Converter

    I think 0.3W is not too much, even small packages can dissipate this, or the PCB. The SMPS is bigger issue, I am not sure anyone can guarantee that any converter's radiated or conducted spectra has...
  2. Closed: Re: LDO transient performance enhancement circuit understanding

    Are you sure above figure is simulated next to 2.5V DC supply? I think we should see some minor changes at least between 2.5V and 3.3V values. Try to plot both on the same figure. Or you could...
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    Closed: Re: matching network design question

    If the coupling elements are big enough the matching shouln't be affected too much. Use big choke and big coupling capacitor.
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    Closed: Re: matching network design question

    I don't know or understand how do you imagine the modification. Here is what I would do:
    1. delete the PMOS and move L1 between NMOS drain and VDD
    2. create an NMOS bias circuit: series IDC source...
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    Closed: Re: matching network design question

    Did you hear about this new stuff, so called operating point? Browse for it. Your NMOS is technically closed, the PMOS is rather a resistor than transistor.
  6. Closed: Re: LDO transient performance enhancement circuit understanding

    Could you show an open-loop gain plot? It is stability issue, you have to improve stability. You have to find which transistor enters triode region when you apply low supply. And make surre these...
  7. Closed: Re: LDO transient performance enhancement circuit understanding

    how much is the minimum and maximum supply voltage do you want? choose transistors which are fit for both. or choose a simplier LDO. or if it is for learning purpose simply don't use low supply.
  8. Closed: Re: LDO transient performance enhancement circuit understanding

    At every low supply voltage moment there is some "noise" on the output. I think it tells that your circuit is unstable at lower supply voltages. Simulate stability with different supply voltage...
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    Closed: Re: How to design RF mixer

    It is not enough specification. Collect how much are noise figure, input/output impedance, 1dB compression point, conversion gain, single or double balanced mixer.
  10. Closed: Re: LDO transient performance enhancement circuit understanding

    I don't have, I only suggest to add capacitors in paralel with the gate-source of M2 and M10. Or add series resistor with the gates, maybe the combination of them. And don't use minimal length for...
  11. Closed: Re: LDO transient performance enhancement circuit understanding

    Why don't you filter the constant-Gm bias circuit? And you have uA consumption, PSRR is strongly frequency dependent, these 2 things together result above. No surprises.
  12. Closed: Re: Fully Differential Amplifier to drive Capacitive Load and Resistive Load

    Your OpAmp load impedance will be less .... than, how much? Negative feedback around the OpAmp decreases output impedance of the OpAmp, I am not sure it is not enough for you to drive the quasi...
  13. Closed: Re: Fully Differential Amplifier to drive Capacitive Load and Resistive Load

    1. I would do the same, design a mixer first, and model a drive opamp to see how the OpAmp should behave.
    2. I am almost sure it is not true for every class AB fully-differential OpAmp that they...
  14. Closed: Re: cmos differential mode equvalent circuit

    Yes, everything is written down and explained in the literature which you are curious about, please read it before write anything. But the point is that when common-mode gain is analised the drains...
  15. Closed: Re: cmos differential mode equvalent circuit

    In diff. mode a simple voltage conrolled current source is the small signal equvivalent model with resistive and capacitive load:
    Gm=Gm2,3 RL=1/(Gds2+Gds4) CL~Cds4+Cdg4+Cdb4+Cdb2+Cds2+Cdg2
    If M4 is...
  16. Closed: Re: Switch size in a resistive trim network ?

    Gate pull-up/down is done by devices with minimal length and relatively small width, not wider than 1um. To make it stronger and more confident the multiplier of the devices can be increased, but one...
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    Closed: Re: Noise Source generator Circuit

    Any single resistor has thermal noise with gaussian probability density function, but noise is not a single frequency. Do you need 6HGz bandwidth for the power spectral density? What would you like...
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    Closed: Re: common mode feedback question

    yefj, you have basic problem with understanding what common mode feedback does. It has no connection to mismatch of currents, CMFB sets/tunes both currents in a way that the main OPAMP will operate...
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    Closed: Re: folded cascode with gm/id

    M1 is half of the diff.pair, so its current is half of the tail current. Thus M3,M4 have a 80uA current. You have to know the ratio of M11/M4 ratio to know how much is the current of M11, which...
  20. Closed: Re: Switch size in a resistive trim network ?

    Yes, it means. Also, no, don't place R to the top. It is more effective if you can shunt R (the samllest resistance unit value) with the lowest NMOS. The lowest NMOS can produce the lowest Ron to...
  21. Closed: Re: Switch size in a resistive trim network ?

    Use minimum L, and choose the minimal W with the following conditions:
    - lowest gate voltage applied
    - slow-slow (SS) process
    - cold temperature (but maybe the hottest temp is also recommended to...
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    Closed: Re: Fast amplifier using one stage OP AMP

    How much is the expected rising/falling time value? Why do you need 5V amplitude, what is your load? Any other specifications (consumption, delay, etc.)?
  23. Closed: Re: Optimum strategy to layout MOSFET cascoded mirror

    1. first approach is pretty good, I suggest it. Match mirrors and cascode devices separately is more effective. Cascodes and mirrors are not the same size usually, why would you match them together?...
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    [SOLVED]Closed: Re: Down-conversion Mixer

    You are not wrong, active can produce more noise, but if you don't gain at the begining of the amplifier chain, the following much more noisy circuits will have bigger contribution. Passive mixer's...
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    [SOLVED]Closed: Re: Down-conversion Mixer

    Active will give much better noise figure, that is why so popular, consumption is not a trade-off if you need -110dBm sensitivity for the receiver chain.

    Actually I don't know, but big advantage...
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