Every amplifier needs a DC power supply in order to provide the necessary energy for the amplification.

The Op-Amp has a double power supply voltage: Valim+ and Valim-.

Generally, these voltages are symmetrical: Valim- = - Valim+ (for example : +15/-15V, +12/-12V, ….)

Nevertheless, this is not always the case: it is not uncommon to have Valim- = 0 (0/9V, 0/5V, …)