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Regenerative Radio Receiver Circuit

Discussion in 'Electronic Design' started by iiiijjjj, Aug 28, 2012.

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  1. iiiijjjj

    iiiijjjj Guest

  2. Tauno Voipio

    Tauno Voipio Guest

    You nearly made it:

    Regens *should* not oscillate (but they occasionally do).
  3. spamtrap1888

    spamtrap1888 Guest

  4. iiiijjjj

    iiiijjjj Guest

    I guess an interesting point is that the (AC linked) differential pair has a tanh input amplitude versus gain curve. The requirement that the transistors be matched in the usual (DC linked) long tail pair is a DC biasing only requirement. The two transistors in the AC linked version can be very different and still give symmetrical behavior. Anyway the slightly compressive tanh response allows for a smooth transition into oscillation with increasing positive feedback. A lot of circuits on the internet use FET's for regeneration. There you have to hope that you can bias the FET into a region of its operating curve where the gain it provides is compressive (decreasesslightly with increasing input amplitude). Even the well know designs by Charles Kitchin in QEX do not address that problem and are kind of hit and miss.
  5. Tim Williams

    Tim Williams Guest

    Hmm, that can't be right. Surely you meant output vs. input (i.e.,
    transfer function), not input vs. gain? Also, atanh?

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