Analog Interfacing to Embedded Microprocessor Systems, 2nd Edition

Although an opamp can be used as a comparator, it is more typical to use a comparator

IC. These parts are essentially opamps, but they are optimized for use as comparators.

They typically have lower gain than an opamp, but much greater speed. They often have

open-collector outputs, so the output voltage swing can be different from the positive

supply voltage. For instance, the comparator may operate from þ12 V and ground, but the

open-collector output may be pulled to þ5V or þ3:3 V with a resistor, making a logic-

compatible digital output.

Hysteresis

What happens to the comparator output if the two inputs are very close together? Figure

A.4 illustrates ...