![]() The open collector structure depends on external circuitry to make the connection to power and complete the circuit. The output transistor of open collector comparators is characterized by low V CE for switching heavy loads. Very few designers make the mistake of using a comparator as an op amp because most comparators have open collector output. It has a differential analog input and a digital output. ![]() 25.3.1 The ComparatorĪ comparator is a one-bit analog-to-digital converter. An op amp has an output stage that is optimized for linear operation, while the output stage of a comparator is optimized for saturated operation. So-if very little appears to be different in the schematic symbol or the internal workings-what is the difference? But be careful-many newer comparators have bipolar stages that are very similar in appearance to op amp output stages. ![]() The output stage of the comparator is obviously different, in that it is a single open collector. The output stage of the op amp is a bit more complex-which should be a clue that something is different. ![]() The input stages look almost identical, except the inputs are labeled opposite (a fine point that will be discussed later).
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