page_title: Comparator
section_title: Output type
hierarchical_section_title: Comparator / Key specifications / Output type
caption_attribution_description: English: A schematic of a CMOS clocked comparator
context_page_description: In electronics, a comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger. It has two analog input terminals and and one binary digital output. The output is ideally
  A comparator consists of a specialized high-gain differential amplifier. They are commonly used in devices that measure and digitize analog signals, such as analog-to-digital converters, as well as relaxation oscillators.
context_section_description: Because comparators have only two output states, their outputs are either near zero or near the supply voltage. Bipolar rail-to-rail comparators have a common-emitter output that produces a small voltage drop between the output and each rail. That drop is equal to the collector-to-emitter voltage of a saturated transistor. When output currents are light, output voltages of CMOS rail-to-rail comparators, which rely on a saturated MOSFET, range closer to the rail voltages than their bipolar counterparts.
  On the basis of outputs, comparators can also be classified as open drain or push–pull. Comparators with an open drain output stage use an external pull up resistor to a positive supply that defines the logic high level. Open drain comparators are more suitable for mixed-voltage system design. Since the output is high impedance for logic level high, open drain comparators can also be used to connect multiple comparators to a single bus. Push-pull output does not need a pull up resistor and can also source current, unlike an open drain output.
caption: A Low Power CMOS Clocked Comparator
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