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Pulse and Digital Circuits by Manmadha Rao G., Rama Sudha K., Venkata Rao K.

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4.4 COMPARATORS

An amplitude comparator is a circuit that tells the time instant at which the input amplitude has reached a reference level. A comparator is shown in Fig. 4.24.

Ideally, in this comparator:

 

vo = 0 for t < t1

vo = V for tt1

The amplitude of the output abruptly rises from 0 to V at t = t1, t1 is the time instant at which vi reaches VR.

4.4.1 Diode Comparators

In this section, we discuss two types of diode comparators—pick-off and break-away diode comparators.

Pick-off Diode Comparators. A simple diode comparator circuit is shown in Fig. 4.25. A base clipper is used as a comparator. The input now is a ramp and VR is the reference voltage. The circuit is required to tell the time instant at which the input reaches VR.

FIGURE ...

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