 Welcome to Op-Amp Comparator. There are several different ways in which a 741 operational amplifier, shown below, operates. The type of function it performs is determined by how components are connected externally to the Op-Amp and the types of components that are connected externally to the Op-Amp. When there are no components connected to the Op-Amp, it operates as a comparator. The Op-Amp compares the voltage applied at one input to the voltage applied at the other input. Any difference between the voltages, even if it is small, drives the Op-Amp into saturation. When the voltages supplied to both inputs are of the same magnitude and the same polarity, the Op-Amp output is 0 volts. The saturation voltages can be either positive or negative. These output voltages produced by the Op-Amp are from both the negative and positive voltage power supply terminals. The saturation voltage is approximately 80% of the supply voltage value. When the voltage applied to the non-inverting input is more positive than the inverting input, the output voltage will be at positive saturation. When the voltage applied to the inverting input is more positive than the non-inverting input, the output voltage will be at negative saturation. Note that if the supply voltages are positive 6.25 volts and negative 6.25 volts, the saturation voltages will be 80% or negative 5 volts and positive 5 volts. Some comparator applications require that the voltage produced at the output be of only one polarity. For example, suppose only a positive voltage is desired. By connecting the negative power supply terminal to ground, it will produce a 0 volt output when the inverting input is more positive than the non-inverting input, a positive saturation voltage when the non-inverting input is more positive than the inverting input, and a 0 volt output when the same voltage values are at both inputs. Let's look at the following input voltage combinations to observe how the Op-Amp responds. You have completed this activity, Op-Amp Comparator.