Circuits often incorporate a compromise between a short RC time constant (for self-adjustment
purposes) and a long RC time constant for less distortion. A point to observe is that the reverse resistance
of the diode sometimes replaces the, physical resistor in the discharge path of the capacitor.
Positive-Diode Clamper With Bias
Biased clamping circuits operate in exactly the same manner as unbiased clampers, with one
exception. That exception is the addition of a dc bias voltage in series with the diode and resistor. The
size and polarity of this bias voltage determines the output clamping reference.
View (A) of figure 4-19 illustrates the circuit of a positive clamper with positive bias. It can be
identified as a positive clamper because the cathode of the diode is connected to the capacitor. Positive
bias can be observed by noting that the negative side of the battery is connected to ground. The purposes
and actions of the capacitor, resistor, and diode are the same as in the unbiased clamper circuit just
Figure 4-19A.Positive clamper with positive bias.
Figure 4-19B.Positive clamper with positive bias.