This page provides basic information about voltage comparator integrated circuits and is to act as reference material for other circuits. The circuits shown are based on the LM339 Quad Voltage Comparator chip or the LM393 Dual Voltage Comparator chip. These devices are functionally identical. The LM311 Voltage Comparator can be used for these applications as well and also has a number of unique features.
An integrated circuit "Voltage Comparator" is equivalent to an Operational Amplifier, Such as the LM358 or LM324, with two NPN transistors added to the output of each amplifier. (Refer to the above schematic.) This arrangement produces an "