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Recent content by arebee

  1. A

    Will a noise-free oscillator produce sustained oscillations?

    Someone has probably already answered this, but here's my contribution. No. Assuming zero IC's, it'll remain at its equilibrium point if there's no input, even if the equilibrium point is unstable. Adding noise is (usually) modeled as adding an input at some point in the system (assuming its...
  2. A

    Designing matching network for high collector/drain Zout

    Yes, I was using a common base for stability. I did some testing and a common base seems to have a higher y21 than a cascode but a slighly higher y12. The trade off of reduced y21 for reduced y12 versus a common emitter seemed reasonable. I did try a common emitter before but alignability and...
  3. A

    Designing matching network for high collector/drain Zout

    Sorry, I meant to say common-base. (With a common emitter and Rs=50 ohms I get around |Zout|=400 ohms, but a common base gives me |Zout|=120k ohms)
  4. A

    Designing matching network for high collector/drain Zout

    Hi. I am designing a tuned common emitter RF amplifier at about 100 MHz. How does one match the high collector output impedance to a low load resistance? I did a simulation and the collector impedance is rather large, about 100 kohm. How do you match this to say a 50 ohm load? Is it...
  5. A

    Is matching source and amplifier Zin always necessary?

    khouly, I understand matching in a LNA, but for a gain stage don't you want maximum input voltage (as opposed to power)? Imagine if the source impedance Rs is purely real and the amplifier input impedance Rin is also real. If Rin=Rs then you "waste" half the input voltage and the amplifier...
  6. A

    Is matching source and amplifier Zin always necessary?

    "Conjugate matching the amplifier input will give you the largest voltage swing at the input, and therefore the largest input power." Why would you want the largest input power in say an common gate amplifier? Don't you want the largest input voltage in that case?
  7. A

    Is matching source and amplifier Zin always necessary?

    For a small signal amp, don't you want maximum voltage rather than maximum power at the input for maximum power output (e.g. a common gate stage)?
  8. A

    Is matching source and amplifier Zin always necessary?

    I understand that matching the output impedance of an amplifier to the load will supply the most power to the load. But is it always necessary to match the input impedance of an RF amplifier to the source impedance? Even when reflections aren't an issue? Won't more power be delivered to the...
  9. A

    How to analysis poles and zeros in Analog cxt design?

    Poles and zeros This book has a new, easy method for finding poles and zeroes from various networks: https://books.google.com/books?vid=ISBN0521624428&id=DYgS4nkJ5W8C&pg=PA1&lpg=PA1&dq=fast+analytical+techniques&sig=UHtZtrHlLjk5l_p5hydDfu9JQPs I highly recommend it.
  10. A

    Design of a simple double tuned BJT amplifier

    Thats what I thought, but that leads to some pretty big capacitors. I was hoping there was a more elegant solution.
  11. A

    Design of a simple double tuned BJT amplifier

    Hi. I've been studying stability and alignment of simple amplifiers with tuned circuits (LC tanks) at the input and output (e.g. a simple common emitter with a grounded emitter) and I have a few questions. I noticed in simulations that the input capacitance Cbe is proportional to the bias...
  12. A

    2.4 GHz DSS cordless phone data rate

    +cordless phone +data rate Hi. I'm looking for some technical specs on DSS cordless phones. In particular the modulation parameters, e.g. bitrate, bandwidth, etc. Can anyone help? Regards
  13. A

    Need help with this FM detector circuit

    Did you get that circuit from this page: **broken link removed** ? Anyway, I recommend the book "Communication Circuits: Analysis and Design" by Clarke and Hess. It has a very thorough analysis of this circuit and many other analog communication circuits.
  14. A

    Mathmatica, Mapple, Mathlab or nay --> Which once to use?

    Re: Mathmatica, Mapple, Mathlab or nay --> Which once to I recommend Derive if you don't wanna spend time learning Maple or Mathematica. Very easy to use, mostly point and click. 2d/3d plotting is especially easy as everything's laid out in a toolbar. Does symbolic integration/differention as...
  15. A

    measure bjt transistor using analog multimeter

    using analog multimeter to measure current If your meter has hfe measuring function (most digital ones do, some analog ones do too) then you could just try every possible pin combination (BJT's only of course) until you get a reasonable hfe reading (~100 typically).
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