The 741 op amp comparator circuit is a simple and popular circuit that is used to compare two input signals and produce an output signal that indicates the relative magnitude of the inputs. The circuit uses the LM741 operational amplifier, which is a widely used and versatile op amp with a wide range of applications.
We can have two types of op-amp comparator circuit. One is over voltage op-amp comparator circuit and the other is under op-amp comparator circuit.
Over voltage 741 op-amp comparator
An over voltage op-amp comparator has its inputs connected to the positive terminal of the op-amp and the the negative terminal is biased using two resistors(or one resistor and the other zener diode) at a voltage called reference voltage. When the input signal voltage Vin is higher than reference voltage Vref than the output Vout is high.
Shown below is circuit diagram of over voltage 741 op-amp comparator.
The resistors R2 and R3 are each 10KOhm and if the supply voltage is 5V then the reference voltage is 2.5V. So if the input signal has voltage higher than 2.5V then the output is high. Shown below shows how the over voltage 741 comparator circuit works.
It can bee seen that when the input voltage is below 2.5V the output voltage is 0.96V and when the input voltage is higher than 2.5V the output signal voltage is 2.28V.
Under voltage 741 op-amp comparator
In the under voltage 741 op-amp comparator, the input voltage is applied to the negative terminal of the op-amp and the reference voltage is set at the positive terminal of the op-amp as shown below.
In the above under voltage LM741 op-amp comparator circuit diagram, the resistors R2 and R3 forms a voltage divider which is connected to non-inverting terminal of the op-amp. This voltage divider is used to set the reference voltage to 2.5V. The input signal is applied to the inverting input of the op-amp.When the input voltage Vin is less than Vref then the output is high. This following shows operation of under voltage 741 op amp comparator.
Applications of 741 op amp comparator
The 741 op amp comparator circuit has a wide range of applications,
including in analog-to-digital converters, signal detection circuits,
and alarm systems. In analog-to-digital converters, the comparator is
used to compare an analog input voltage with a reference voltage and
produce a digital output signal. In signal detection circuits, the
comparator is used to detect when a signal crosses a certain threshold
level, and in alarm systems, it can be used to detect when an input
signal exceeds a certain level, triggering an alarm or other response. Another example is Light and Darkness sensor Circuit where LDR sensor is connected as input to detect light intensity in a room and automatically turn on or off a switch. Also comparator circuit can be used to build Astable Multivibrator with Operational Amplifier.
Overall, the 741 op amp comparator circuit is a simple and versatile circuit that can be used in a wide range of applications. Its ease of use and reliability have made it a popular choice for hobbyists, students, and professionals alike.
