Simply we can say that a gate will have two interpretation depending on positive and negative logic. Those can be represented by positive logic input and negative logic inputs.
Example,
- 1 – Higher input
- 0 – Lower input
And in electronics, we use two level of voltages 0V and +SV dc voltage. We can say 0 for low voltage and 1 for high voltage (+SV dc). This system of digital logic is called positive logic
Positive logic inputs and outputs are also called active high.
Negative logic inputs and outputs are called active low. Input and output polarity is indicated by a bubble or triangle.
For example, the following shows a positive logic AND gate and a negative logic OR gate.
But the system of digital logic where binary 0 represents higher voltage and binary 1 represents low voltage is called negative logic.