Rest in all the cases, the output will be 0 (Low) and the LED will be OFF. Meaning, there will be a straight line current path from VCC (+5V power supply) to the LED and further to the ground. ![]() when there is a voltage supply at the base terminal of both the transistors. the output is 1 (High) only when both the inputs are 1 (High) i.e. ![]() Similarly, the circuit above would make the LED glow i.e. Here we will be using the transistor as a switch and so, when a voltage is applied through a Collector terminal of the NPN transistor, the voltage reaches the Emitter Junction only when the Base Junction is having a voltage supply between 0V and Collector Voltage. The same circuit when built using the above mentioned hardware components, the circuit would look something like in the image below. The same could be seen in the video where I would use the wires as a switch connected to the base terminal for both the transistors. If you do not have the push buttons with you, you can also use wires as a switch by adding or removing them whenever required (instead of pressing the swtich). The Transistors used in this tutorial are BC547 NPN Transistor and were added with all the above-mentioned components in the circuit, as shown below. The below diagram represents the above-explained circuit to build an AND gate using NPN Transistor. The inputs A & B are connected to the base terminal of Transistor 1 and Transistor 2, respectively and the output Q goes to the positive terminal LED. The circuit represents both the inputs A & B for the AND gate and Output, Q which also has a +5V supply to the collector of the first transistor which is connected in series to the second transistor and an LED is connected to the emitter terminal of the second transistor. One LED (Light Emitting Diode) to check the output.Two 10KΩ resistors & one 4-5KΩ resistor.(You can also use PNP transistor if available) The list of components required to build an AND gate using an NPN transistor are listed as follows: The logic of an AND gate is explained above already and to build an AND gate using a transistor we will follow the same truth table shown above. This article will explain to you, how to build AND Gate circuit using transistor. The circuit symbol for each of them can be seen below. The device can be used as a switch and also as an amplifier to change the values or control the passing of an electrical signal.įor building an AND logic gate using a transistor we would be using BJT transistors which can be further classified into two types: PNP and NPN – Bipolar Junction Transistors. TransistorĪ transistor is a semiconductor device with three terminals that can be connected to an external circuit. Hence, for an AND Gate the output is HIGH only when both the inputs are HIGH. The equations output can be easily explained using the AND Gate Boolean Equation, which is Q = A x B or Q = AB. The relation between input and output values can be explained using the AND Gate Truth Table shown below. AND Logic GateĪND logic gate is a D-shaped logic gate with two inputs and one single output, where the D shape in between the input and output is the logic circuit. ![]() But the focus of this article will be on the AND Gate because later we would be building an AND Gate using a BJT transistor circuit. There are many different types of logic gates and each of them has a different logic which be used for different purposes. They state the relation between every input and output of a system using an Arthmetic logic. From the basic Flip-Flops to Microcontrollers Logic gates form the underlying principle on how bits are stored and processed. Logic Gates are the basics of a many digital electronic circuit. Similarly a Flip-Flop can be built by using a combination of Logic Gates and the Logic Gates itself can be built by using a few Transistors. Like an Operational Amplifier or 555 Timer IC is built by combination of many Transistors, Flip-Flops, Logic Gates and other combinational digital circuits. As many of us know an Integrated Circuit or IC is a combination of many small circuits in a small package which together performs a comman task.
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