What is negative voltage? Introduction to negative voltage Wikipedia
Negative voltage is relative. First of all, we need to have a reference. For example, if the existing voltage requirement is 4.0V, then higher than 4.0 is positive voltage, and small is negative voltage. There is a power supply module that can output both positive and negative voltages at the same time, and that's it. It's not about how much voltage can really be output.
Positive and negative voltage operating principle
The positive and negative voltages are determined by the reference zero point (zero scale, or "ground"). The most classic zero-scale is the earth, that is, the earth's crust. But not all zero-scale is earth, because the zero-scale in the circuit diagram is actually set by the designer. The power supply is a device that provides electromotive force, there is a potential difference between its positive and negative poles, such as a 5V power supply, the voltage difference between its positive and negative poles is 5V, generally when used, 5V is connected to the positive pole of the electrical appliance, the negative electrode is connected to the negative pole of the electrical appliance, and the negative electrode can be regarded as a reference ground when analyzing, that is, a reference zero scale. At this time, this power supply is called a positive power supply, because its positive voltage relative to ground is 5V. If two identical 5V power supplies are connected in series (similar to two series batteries in a flashlight), a wire is led to the two power connection points, and the voltage of this wire is considered to be 0, then the positive terminal voltage of the series power supply is 5V, and the negative pole is -5V relative to the 0 voltage, and the negative power supply is born in this way. Some chips need to provide both positive and negative power supplies to work normally, the most typical is a dual-power operation amplifier, we sometimes need to get a sine wave, the sine wave is required to be up and down zero voltage constantly changing (that is, the midpoint is 0V), this time must use positive and negative power supplies. However, it should be pointed out that the positive and negative voltages are relative to the reference voltage in the circuit drawing (reference 0 level, not necessarily the earth), and there is no reference that does not matter whether it is positive or negative. Sometimes, when you design a reference point voltage that is much higher than the earth (the special term is called "floating"), the positive and negative voltages in the circuit diagram may still be a fairly high voltage (relative to the earth), and you should be careful when using it.