Digital Inverter or Analogue Inverter?
I think you have been confused by the overloading of the term "inverter".

A UPS (uninterruptable power supply) converts a low d.c. battery voltage to an approximation of a sinusoidal mains (high) voltage. Since it is the opposite of the common power supply design which converts high voltage mains to low voltage d.c., it can be called an inverter. But it has nothing to do with analogue and digital inverters.

A digital inverter is also called a NOT gate and simply outputs the boolean opposite of the input. Voltage levels are defined by the logic family and supply rails.

An analogue inverter is an amplifier which produces opposite phase signals to the input, so as the input goes up, the output goes down.