![]() That means this junction again becomes a potential divider, whose voltage level this time is not fixed because the LDR value cannot be fixed and will vary with the ambient light conditions. The pin #3 is connected at the junction of the LDR pin and a preset terminal. The sensing voltage which is to be monitored is applied to pin #3 of the IC, in our example it is via an LDR. Therefore referring to the junction voltage of the resistors R1/R2, this voltage becomes the reference voltage at pin #2 which means the IC will monitor and respond to any voltage that might go above this level. If the supply voltage is well regulated, the above voltage level will also be well fixed and therefore can be used as the reference voltage for the pin #2. This arrangement of the resistors is called a potential divider, meaning the potential or the voltage level at the junction of these resistors will be approximately the half of the supply voltage, so if the supply voltage is 12, the junction of the potential divider network will be 6 volts and so on. Now as discussed earlier, pin #2 of the IC is connected at the junction of two resistors whose ends are connected to the power supply positive and negative rails. The above couple of pin connections powers the IC so that it can carry on with its intended functions. We can see that the Pin #7 of the opamp which is the +supply pin is connected to the positive rail, similarly its pin #4 which is the negative supply pin is connected to the negative or rather the zero supply rail of the power supply. Looking at the circuit diagram we find the circuit configured in the following way: Therefore if the voltage which is to be monitored goes above or falls below the fixed reference threshold voltage, the output reverts state or changes its original condition or changes its output voltage polarity. ![]() The monitoring of the above voltage is done with reference to the fixed voltage that's been applied to the other complementary pin. When used as a comparator, one of the pins out of the two is applied with a fixed reference voltage while the other pin is fed with the voltage whose level needs to be monitored, as shown below. ![]() #COMPARATOR RELAY CIRCUIT PLUS#The two input pins of an op amp are called the inverting (with a minus sign) and the non-inverting pin (with a plus sign) become the sensing inputs of the op amp. REMEMBER, THE VOLTAGE ON THE INPUT PINS SHOULD NOT EXCEED THE DC SUPPLY LEVEL OF THE OP AMP, IN THE ABOVE FIGURE IT SHOULDN'T EXCEED +12 V In the proposed op amp comparator design, basically two different voltage levels are used at the input pins for comparing them, as shown in the below diagram. Since in electronics we are primarily dealing with voltages and currents, these factors become the sole agents and are used for operating or regulating or controlling the various components involved. Here we are discussing one of the simple application circuits of this IC where it is being configured as a comparator, no surprise the following applications can be modified in numerous different ways as per the user preference.Īs the name suggests, opamp comparator refers to the function of comparing between a particular set of parameters or may be just a couple of magnitudes as in the case. We've been using an op amp IC probably since we started learning electronics, I am referring to this wonderful little IC 741, through which virtually any comparator based circuit designing becomes feasible. Op Amp Comparator as Over Current Indicator.Op Amp Comparator with High Value Input, Regenerative Switching.Op amp Comparator with High Voltage Input. ![]()
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