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Dual Biased Emitter Follower

Discussion in 'Electronic Design' started by David White, Feb 16, 2012.

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  1. David White

    David White Guest

    I posted this to sci.eelctronics.basic, where it probably belongs, but
    things seem a bit quiet over there at the moment.

    Based on previous advice from the groups, I have attempted
    to revise our circuit utilizing a complimentary pair, and diodes to
    establish a 1.4V DC offset between the two output signals.

    Here is the schematic, if anyone would please be able to comment on

    If this sounds familliar, there are several of us cooperating on the
    same project, none obviously any more gifted than the other.

    Thank you,

    David White
  2. mike

    mike Guest

    +1 on the "what are you trying to accomplish?

    What are the characteristics of the two different inputs?
    And what does it mean to have an offset between two different "audio
    sine wave" inputs that are half-wave rectified?
    And how does the base-emitter reverse breakdown voltage compare the the
    input signals?
    And what do the batteries do?
    If you draw a box around the top half and apply norton's theorm,
    the output current has to be less than the input current by the amount
    of diode current.
  3. David White

    David White Guest

    If I understand correctly, John, if the diodes were removed the
    circuit would work.

    The question is, why are they there?

    As I attempted to indicate on the diagram, the two outputs are meant
    to be floating (dual single wire system), one above and one below the
    grounded battery common by 0.7V.

    IOW one swings 0.7V positive to 9V positive. The other is 9V negative
    to 0.7V negative.

    Putting aside convention, for the moment, the unique point is NOT to
    have them referenced to ground. Perhaps we are going about it the
    wrong way, but we seem to have tried everything else.

    I would like to go ahead and build the circuit if anyone can tell me
    how to give it half a chance.

    How about replacing the diodes with +/- 5V voltage regulators? We
    could use +/- 12VDC rails to compensate for the voltage loss.

  4. miso

    miso Guest

    It looks to me like you are trying to make a class B or class AB output
    driver. Why not look at those circuits first before rolling your own?
  5. David White

    David White Guest

    With diodes removed, I assume one output would swing between +9 and 0
    Volts, and the other -9 and 0 volts. Can we say that much will work?
    The intended circuit is a learning exercise, and, as yet, has no
    practical application.

    The only object is to output two identical signals with no direct
    ground reference to each other or the supply; one being offset
    positively from ground and the other negatively.

    Not being a conventional approach, it appears difficult to get one's
    head around. But I assume it is possible ... somehow.

  6. Phil Allison

    Phil Allison Guest

    "David White"

    ** You have no knowledge of electronics at all - do you ?

    ** Only way to do that involves isolation transformers.

    ** That implies they ARE referenced to each other.

    You show the inputs with a common ground too - contradicting your own

    ** No, it is a fuckwit approach.

    .... Phil
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