The negative voltage generator, also known as NVG, can only source a small amount of current. If a regulator is used on the output, don't expect to get more than 4mA ~ 5mA. But if left unregulated, you can source up to 20mA before the output voltage begins to drop significantly. When using this generator in projects, try to keep the current draw from devices as small as possible so that the negative rail can keep its voltage value. Suppose you have a negative voltage generator circuit, you can do the following things.
Build a single rail dual supply: Using regulators and filtering components, you could make a dual rail supply that takes in a battery voltage and converts it into a 5V and a -5V. If you use a large enough input voltage, you could also make a 12V and -12V line.
Op-Amp Projects: Many op-amp projects require the use of a negative rail.
Audio Projects: Audio components such as speakers work better when they use both positive and negative voltages. You can easily find that the sound is much louder and clearer.
Portable Dual Rail: If you have a system where weight needs to be reduced, it’s better to use a negative voltage instead of two separate supplies.