You can use one or two op-amp from the four or you can also use four at once. The IC contains four high gain operational amplifiers which are independent from each other. It is manufactured in 14 pin DIP package, 14 SOP and other package. LM324 is a famous operational amplifier IC, it is widely used in commercial devices and also used by electronic hobbyists, engineering students, engineers, and tinkerers around the world. Output of IC's Forth Operational Amplifier Non Inverting Input of IC's Fotrh Operational Amplifier
Inverting Input of IC's Forth Operational Amplifier Ground / Negative Supply of IC / Negative Supply of Output of IC's Third Operational Amplifier Non Inverting Input of IC's Third Operational Amplifier Inverting Input of IC's Third Operational Amplifier Output of IC's Second Operational Amplifier Non Inverting Input of IC's Second Operational Amplifier Inverting Input of IC's Second Operational Amplifier Positive Supply of IC / Positive Supply of Non Inverting Input of IC's First Operational Amplifier Inverting Input of IC's First Operational Amplifier Output of IC's First Operational Amplifier Thanks to its standard pinout structure.