25-08-2017, 09:32 PM
Clippers And Clampers
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Clippers
Clipping circuits (also known as limiters, amplitude selectors, or slicers), are used to remove the part of a signal that is above or below some defined reference level. We’ve already seen an example of a clipper in the half-wave rectifier – that circuit basically cut off everything at the reference level of zero and let only the positive-going (or negative-going) portion of the input waveform through.
To clip to a reference level other than zero, a dc source (shown as a battery in your text) is put in series with the diode. Depending on the direction of the diode and the polarity of the battery, the circuit will either clip the input waveform above or below the reference level (the battery voltage for an ideal diode; i.e., for Von=0).
A parallel-biased clipper is a circuit that clips the positive and negative-going portions of the input signal simultaneously. This is designed by using two parallel diodes oriented in opposite directions – note that it is very important that the diodes are oppositely oriented (think voltage sources in parallel – a big no-no!). Just as in our previous discussion, the path containing diode D1 will provide the upper limit with reference level VB1+VON (with the VB1 polarity shown) and the path containing D2 will provide the lower limit with reference level VB2+VON (with the VB2 polarity shown). An example of this type of clipper, with the resulting output waveform is shown below (Figure 3.45 of your text