![]() The output of the LM741 will be drawn high and the LED will turn on.Īnd this is a basic, yet effective, circuit of how an LM741 operational amplifier can function as a comparator to compare voltage levels and make decisions based on these levels.Short circuit protection Excellent temperature stability Internal frequency compensation High Input voltage range Null of offset Therefore, the voltage will be greater than Therefore, a lot of voltage will fall across it. If the photoresistor is exposed to darkness, it will have a very high resistance. Therefore, the output will be drawn low down to ground and the LED will not light up. Voltage divider will be less than the reference voltage. Therefore, the voltage coming from the photoresistor Since the resistance is low in bright light, very little voltage falls across the photoresistor. According to ohm's law, voltage that falls across a component is directly related to its resistance value (Voltage=Ĭurrent * resistance). Photoresistor is exposed to bright light, it will have a very low resistance. In this case, we are comparing a reference voltage set by the potentiometer and the voltage from the voltage divider between the photoresistor and the fixed resistor. This circuit works by exploiting the fact that an LM741 operational amplifier can function as a comparator. Now that we see how a LM741 can function as a comparator, let's see and examine an actual circuit in which an LM741 is used as a comparator.īelow is the schematic of a night light circuit using the LM741 as a comparator. If the noninverting voltage is greater, the output will be drawn down to V. ![]() As explained, if the inverting voltage is greater than the noninverting, the output will be drawn up The last terminal we use is the output terminal. Depending on which is greater (or less) determines what occurs at the output terminal. ![]() ![]() These are the terminals where we place both voltages to compare which voltage The inverting terminal and the noninverting terminal are the 2 input terminals. Thus, the voltages we supply to these terminals are really biasing for our output. ![]() When the inverting input voltage is less than the noinverting The inverting input voltage is greater than the noninverting input voltage, the output will be V+. This is so that the IC has the power it needs to operate. V- is either connected to ground or receives negative voltage. This power is placed in the terminals, V+ and V. So the LM741, as in any case, needs power in order to operate. The LM741 is an operational amplifier IC that can function as a comparator. You can see now how a comparator compares voltage values and based on these value levels perform different actions. For example, if it goes above the reference level, an LED turns on. If it goes below it, we can make the circuit performĪ different action. If it goes above it, then we can make the circuit perform a certain action. If we have a reference voltage (set at some value), and we have a variable voltage, using a comparator, we can tell whether the variable voltage goes above This is usually from some type of sensor such as to measure light, heat, fluids, etc. And usually the other voltage is unknownĪnd variable. Usually, a comparator will have one input that has a set (and known voltage). In this way, you can see how a comparator is used to check voltage levels. Op amp will be low (it will be whatever voltage is supplied to the V- terminal). If the voltage goes below 5 volts, then the output of the Of the LM741 will be high (it will be whatever voltage is supplied to the V+ terminal of the op amp). If it goes above 5 volts, then the output LM741 is 5V and the other is a voltage divider circuit, we can tell whether the other voltage goes below or above the 5 volts. Make decisions based on which input has larger voltage.Ĭomparators are very useful for many different types of electronic circuits.įor example, say that we are using the LM741 op amp as a comparator and we have 2 inputs we are monitoring. We will go over how the LM741 operational amplifier IC can be used as a comparator.Ī comparator is an electronic device that can compare voltages that are on its inputs to determine which is larger or which is smaller. How to Use the LM741 Op Amp as a Comparator ![]()
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