To understand this answer, you should first read my answer to this question:
An invertierer (non-gate) is the simplest logic gate in digital electronics with only one input (ON) and one output (OFF).This gate inverts the signal at the entrance to its opposite at the exit. That is, when PLUS arrives at the input, MINUS appears at the output and vice versa. The gate consists of two so-called complementary transistors (I am talking about complementary MOS logic (CMOS) here).
A transistor is a component that has an almost infinite resistance when there is no signal on its center part, which we will figuratively call the “heart” of the transistor here.The heart can be PLUS- or MINUS-sensitive. If a sufficiently strong minus signal arrives at the minus-sensitive (N) heart, the resistance of this transistor is practically zero, i.e. it is fully conductive. The opposite is true for the other transistor (NPN).
Please look at this picture:
When we connect the input to the lower minus rail (with which we simulate the arrival of a maximum strong minus signal), the upper PNP transistor becomes conductive, so that the plus descends from the top of the output.
This means maximum blowing at the output. However, when we connect the input to the upper plus rail (using which we simulate the arrival of a maximum strong plus signal), the lower NPN transistor becomes conductive, so that the minus rises from below to the output. This means maximum suction at the output. So, from the minus at the entrance we got a plus at the exit and vice versa.
In both cases, the same force intensity is present at the output, only in the first case it is bubbles, in the second case it is sucking.
The biggest mistake of digital electronics, which I am talking about in my answer above, is this: suppose the battery is 5 volts.In this case, today’s electronics say that the upper rail is +5V and the lower rail is 0V (so-called ground, ground). When we connect the ON to the lower rail, she says that we have +5V on the “OFF” (that’s “One”). However, when we connect the “ON” to the upper rail, it says that we have 0V or NO SIGNAL at “OFF” (that’s “zero”).
Further details can be found here https://newtheories.info
P.S. Please also note this: if there is a minus signal with a strength of, for example, 1V at the input, then it is strong enough to drive the PNP-MOSFET into saturation (full conductivity), but still has a significantly lower strength than the case if the input is a minus signal of 0V.