LM311 Comparator Night Light Circuit The schematic diagram of the night light circuit is shown below. The LM311 comparator can have other output arrangements as it has both an open collector and open emitter on the output transistor. 3. First we will build a “low battery” circuit. There is also the LM3915 - Dot/Bar Display Driver. The 2 inputs, out of which one is  a reference voltage (Vref) is compared with each other. The following three diagrams are some examples of Dual voltage circuits. The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs or vacuum fluorescent displays. The non-inverting input of this circuit is connected to the point requiring sensing. How the Flip Flop works. The second input is connected to a reference voltage representing the safe level. Saved from learningaboutelectronics.com. Comparator Circuit A comparator circuit compares two voltages and outputs either a 1 (the voltage at the plus side; VDD in the illustration) or a 0 (the voltage at the negative side) to indicate which is larger. A red color indicates negative voltage. The width of the loop outlined by an OFF-ON-OFF cycle is the input hysteresis voltage. Notice that the second comparator section in the time delay circuit shares the same reference voltage input as the first. It is called a non-inverting comparator circuit as the sinusoidal input signal Vin is applied to the non-inverting terminal. Current WILL NOT flow through the open collector when the voltage at the PLUS input is higher than the voltage at the MINUS input. 2. This circuit will illuminate an LED whenever the 12 volt line goes below 11 volts. Short timing functions such as a pulsed outputs or time delays can also be created with one or two comparator sections. The comparator can be called a voltage level detector, as for a fixed value of Vref, the voltage level of Vin can be detected. When the value of the input voltage Vin is greater than the reference voltage Vref the output voltage Vo goes to positive saturation. In theory the REFERENCE and INPUT voltages can be anywhere between zero and the supply voltage but there are practical limitations on the actual range depending on the particular device used. It is called a inverting comparator circuit as the sinusoidal input signal Vin is applied to the inverting terminal. Thus, an op-amp operating in open loop configuration will have an output that goes to positive saturation or negative saturation level or switch between positive and negative saturation levels and thus clips the output above these levels. This circuit can sequentially indicate 4 voltage levels. The circuits shown are based on the LM339 Quad Voltage Comparator or the LM393 Dual Voltage Comparator. Comparator – Designing 1-bit, 2-bit and 4-bit comparators using logic gates A Comparator is a combinational circuit that gives output in terms of A>B, A