Practical Voltage Comparator Circuit Design

Practical Voltage Comparator Circuit Design:

In this post,  we will see how to build the voltage comparator circuit using LM3302. In other words, How to verify the voltage comparator operation of the Comparator  IC?....
Before proceeding further, quickly refresh about the voltage comparator IC LM3302.

Voltage Comparator IC LM3302 Tutorial:

As it name indicates, this device will compare the voltages applied to its input terminals gives the output accordingly.


  • This IC contains four independent voltage comparators.
  • They operate from a single power supply.
  • The supply range will be the minimum of 2V to maximum of 28V.
  • In a crisp manner the operation of the LM3302 IC can be said as follows:
    (1) When the voltage on the non-inverting (+IN) input is greater than the inverting (-IN) input, the output is  HIGH.
    (2) When the voltage on the non-inverting (+IN) input is less than the inverting (-IN) input, the output is LOW.

We will verify this operation by building the following circuit.

  • As shown in the schematic, the 2K, 10K resistors form a voltage divider circuit.
  • By applying the voltage divider rule, the input voltage to the inverting terminal of the opamp will be
    = {15 x [10k/(2k + 10k)]}
    = 12.5V
  • Similarly 10K pot and 10k ohm resistors form another voltage divider circuit.
  • The voltage across the 10k Ohm will be given to the non-inverting input of the opamp.
  • As mentioned in the above paragraph, whenever the voltage at the non inverting terminal voltage is more than the inverting terminal, the output is high.
  • In other words, whenever the voltage across the across the 10k ohm resistor(in the 10k pot, 10k resistor) increases more than 12.5V, the LED will glow.
  • The 1k resistor in the output side of the opamp is known as pull up resistor.

You can build this circuit in a breadboard itself. Instead of only reading about the concept it will be great and understand perfectly if you build this circuit ( and troubleshoot if you required).

Once you are quite familiar the operation of this comparator operation, you can build the monostable vibrator circuit using this IC. That will be discussed in another post.

Once you done this, just disconnect the output side LED, 1k resistor and connect them to the ground. ( remember in that case, the anode of the LED should be connected to the comparator output). Now check the operation again.... 

Voltage_Comparator_CircuitParts required:

IC LM3302 --> 1No
10K POT -->1no
Resistor - 10K --> 2No
Resistor - 2K --> 1No
Resistor - 1K --> 1No
LED -->1No


You may also like to read:
Monostable Multivibrator using 555 Timer IC
555 Timer Based Simple Projects Ideas
Simple LED Flasher Circuit

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