The LM324 series consists of four independent, high gain,internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current..
LM339 - Low Power Quad Op-Amp
Advantages:
High precision comparators
Reduced VOS drift over temperature
Eliminates need for dual supplies
Allows sensing near GND
Compatible with all forms of logic
Power draisuitable for battery operation
Features:
Four Independent Comparators..