LM339 LOW POWER OFFSET VOLTAGE QUAD COMPARATOR

• Low Power Offset Voltage Quad Comparator
• LM339 is designed for use in level detection, low−level sensing and memory applications in consumer, automotive, and industrial electronic applications.

The LM339 is a quad op amp comparator. This means it is made up of 4 independent op amps.This means that up to 4 different input values can be compared. A comparator works by a simple concept. Each op amp of a comparator has 2 inputs, a inverting input and a noninverting input. If the inverting input voltage is greater than the noninverting input, then the output is drawn to ground. If the noninverting input voltage is greater, then then the output is drawn high to VCC. So if the output of an op amp is attached to an LED, the LED will turn on if the voltage at the inverting terminal is greater than the voltage at the noninverting terminal. And the LED will be off when the voltage at the noninverting terminal is greater than at the inverting terminal.
With an LM339, since it has 4 op amps (it is a quad op amp comparator), an engineer can use the 4 op amps to compare 4 values. The output will be drawn high to Vcc for those op amps that have a greater inverting voltage than noninverting voltage. And the output will be drawn to GND for those op amps that have a greater noninverting voltage than inverting.