Question about using power supply
The TL084 has a recommended supply range of \$\pm 5V\$ to \$\pm 15V\$, so if you intend to run a single-ended supply (i.e. the negative supply rail is ground) that means the supply must be between 10V and 30V.

There is no theoretical maximum current rating for the supply, only a minimum current rating; see this question for more details. If you intend to draw 120mA from the power supply, your supply must be capable of providing more than 120mA. Setting the power supply to 10V and 1A is perfectly fine. Running at 20V and 0.5A is perfectly fine. Running at 10V and 0A is not fine because you are below the minimum required current.

Note that op-amps only work as designed when the output and inputs are between the supply rail voltages; you will not be able to build an inverting amplifier with a single-ended supply unless you use a virtual ground. See here for more information.