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differential input??

Discussion in 'Electronic Basics' started by Vexator, Sep 5, 2004.

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  1. Vexator

    Vexator Guest

    what is the differential input in a RF power amplifier?

    Giovanni from Italy
  2. It is very much like any differential input. All inputs require two
    nodes, because any signal voltage has to exist with respect to some
    reference voltage (and any signal current that goes in one path has to
    exit from some other path). Single ended signals use a common node
    (ground) as the second node. Differential signals carry information
    as the difference voltage between two nodes, regardless of the average
    voltage on the two nodes with respect to ground.
    The amplifier responds (ideally) to only the difference voltage
    between the two nodes, and ignores any common (average) voltage.

    A very simple example of a way to convert a single ended amplifier
    input to differential input would be to add an isolating transformer
    to the input. The signal is applied across one winding (that is
    isolated from any ground connection, or has its center tap grounded)
    while the secondary has one end grounded and the other end tied ot the
    single ended amplifier input.
    This works fine for AC signals, but won't work for DC.
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