Comparator OP-AMP (Comparator)

In hardware design uses a comparator circuit, which is one implementation of the op-amp function. One characteristic of the comparator circuit is the absence of feedback from output to input. Another feature that is the Vref on one input and ground.

Comparative Picture Association circuit (comparator)

From the figure above it can be seen the following equation:

The working principle of the comparator is the op-amp IC LM 311 will compare the input voltage (VI) with voltage Vref. Vref can be either positive or negative voltages.
If given a positive voltage on Vref, so when the input wave is in the 0 to-Vref or input wave at a negative cycle, then the output voltage (Vo) Vo max will be made achieve positive and at the input waves are in the 0 to + Vref or wave input on the positive cycle, the output voltage Vo will be made reaching negative max.
If the Vref given negative voltage, so when the waves exceed the negative input voltage (-Vref) the output voltage (Vo) will be made higher (up to a maximum voltage positive output voltage. Shown in the picture below wave output responses to input waveform comparison the reference voltage (Vref).

Figure Shape waves in the Comparator Input (a) and form the output:
(b) the positive Vref
(c) the negative Vref