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CLIPPER CIRCUIT to clip of higher voltages without bias

  1. Oct 31, 2012 #1
    Good Day everyone.

    Is it possible to design a clipper circuit to bias at higher voltage level without using bias voltage?

    For example. to clip at 3.5V for a input signal of 10V sine without using a BIAS VOLTAGE??
     
    Last edited by a moderator: Oct 31, 2012
  2. jcsd
  3. Oct 31, 2012 #2
    It's a little unclear as to what you mean by bias voltage. Usually clipping is achieved by shunting a relatively high impedance signal to a relatively low impedance voltage source through a diode. While you may be able to build a clipper using a zener, perhaps in combination with other diodes, the result won't be as clean of clipping as if you had used a voltage source to set the clipping level.
     
  4. Oct 31, 2012 #3
  5. Oct 31, 2012 #4
    At 3.5V zeners are useless.
    Replace diode and battery with:
    LED's work pretty good.
    Solid state zeners should work good. Such as LM385Z-2.5
     
  6. Nov 5, 2012 #5
    I made once a very good clipper by connecting the emitter of a bipolar transistor to the input, the base to the clipping voltage minus Vbe, and the collector to the ground or a power rail. Precise, strong, very fast. In your diagram's polarity it would be a PNP.

    Though, the base-emitter junction is fragile and breaks down at few volts.

    The solution is to swap the emittor and collector of the (still PNP here) transistor to input at the sturdy base-collector junction. ¡Ole! A bipolar still works that way, albeit with its less good reverse current gain, and is slower.

    If (probably) the ground or negative supply is too far away for the (now) base-emitter junction, use a cascode with a PNP (biased normally) to limit the first transistor's base-emitter voltage to 1V.

    If the reverse beta is too low and the resulting clipping base current uncomfortable for the voltage reference, add a PNP Darlington.

    That makes more cabling than an integrated Zener equivalent, but it's damned fast, and clips more current than the reference can sink.
     
  7. Nov 6, 2012 #6

    NascentOxygen

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    Staff: Mentor

    It depends how close to the ideal you want it ....
     

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