The LM339DT is an N-channel quad comparator (also called voltage comparator) manufactured by STMicroelectronics. It can compare two input voltages and output a digital signal based on whether the two voltages are equal, less than, or greater than one another. This digital signal can be used to control logic circuits and other devices like microcontrollers. It operates from a single power supply ranging from 4.5V to 36V, making it suitable for both low voltage and high voltage applications. The part features a built-in hysteresis of 1.5mV, high noise immunity, fast propagation delay time, and low input bias current. The LM339DT is used in a variety of applications, such as motor control and other automated systems, measuring systems, and circuit emulation.