NAND Gate is the special type of logic gate which is also known as the Universal Gate, because it can be used to implement other basic logic gates like AND, OR, and NOT. It performs NAND(NOT AND) operation between two or more binary inputs and gives output binary signal. This is a combination of AND gate and NOT gate. It gives the output low(0) only when all of its inputs are high(1). In simple words we can say that NAND gate is the opposite (inverted) of AND Gate.
The Boolean expression for the NAND Gate is the complement of logical multiplication of inputs denoted by a full stop. Suppose we have two inputs, A and B and the output is called X, then the expression is
X = (A . B)’
Operation of NAND GATE
NAND Gate takes Boolean values as input and returns
- Returns 1, if all the inputs are 0 or alternative (meaning one is 0, and the other is 1 or vice versa).
- Returns 0, if all inputs are 1
Types of NAND GATE
The NAND gate is classified into three types based on the number of inputs it takes.
2-Input NAND Gate
It is the simple form of NAND gate. In this type of NAND gate, there are only two input values and one output values. There are total of 22=4 combinations of inputs possible. The logic design and Truth table are mentioned below.
3-Input NAND Gate
Unlike the 2 input NAND gate has two inputs, the 3-inputs NAND gate has total of three inputs. The NAND gate can be joined(cascaded) together to form individual inputs of any number. There are total of 23=8 combinations of inputs possible. The Boolean expression of NAND gate is defined as binary operation addition(+).
Multi Input NAND Gate
We can form NAND gate with any number of inputs i.e., n inputs. The output is low(0) only when all of its inputs are high(1). There are total of 2n combinations of inputs possible. When there is NAND gate with multiple inputs but you don’t need to use all of them, then you can connect the unused inputs to the power supply i.e., set them high(1).However instead of connecting directly directly to the power, we can use pull-up resistors. These will helps to stabilize the input without drawing too much current, which helps to prevent changes in the circuit.
Multi Input NAND Gate
NAND Gate in Terms of Transistor
The NAND gate can be constructed using transistors, which are the key blocks of digital electronics. In this transistors acts as a small switches in a circuit, turning on or off based on the signal received from the input. In NAND gate, transistors is used to make sure that the output is low (0) only when all of its inputs are high (1). NAND gate can be implemented by using transistor in various configurations, but a common method is using two NPN transistors connected in series.
Working of NAND Gate in Terms of Transistor
In a transistor-based NAND gate, two or more NPN transistors are connected in series (one after the other). The key concept here is that for the output to be low (0), all the transistors must be on. This means that each input must provide the required signal to turn on its corresponding transistor.
- The positive voltage supply (Vcc) is connected to a pull-up resistor, which is then connected to the output.
- The collector of the first transistor (T1) is connected to the pull-up resistor and the positive supply (Vcc), while the emitter of T1 is connected to the collector of the second transistor (T2).
- The emitter of T2 is connected to ground (0V).
- The inputs, A and B, are connected to the bases of T1 and T2, respectively.
- Both Inputs Low (A = 0, B = 0): When both inputs are low (0), neither transistor turns on, so no current flows from the output to ground. The pull-up resistor keeps the output at a high (1) state. This results in a high output.
- One Input High (A = 1 or B = 1): When either input is high (1), the corresponding transistor turns on. However, since the transistors are in series, current cannot flow all the way to ground unless both transistors are on. The output remains high (1).
- Both Inputs High (A = 1, B = 1): When both inputs are high (1), both transistors turn on, completing the circuit path from Vcc to ground through the transistors. This pulls the output down to a low (0) state.
Applications of NAND Gate
- Universal Gate: NAND gate is called Universal Gate because all the basic logic gates can be formed using them.
- Arithmetic Logic: NAND gates are extensively used in the Arithmetic and Logic Units (ALUs) of a computing device to perform operations like addition, subtraction, etc.
- Used in Decoder and Encoder: NAND gates are also used in Decoder and Encoder circuits to convert a binary code into a set of digital signals and vice versa.
- Used in Multiplexers and Demultiplexers: NAND gates are used in Multiplexers to decide which route a signal should take to reach a single output. The demultiplexer does the exact opposite of this.
- Logical Operations: NAND gates are also used to implement various logical operations.
Advantages of NAND Gate
- It is a Universal Gate: NAND gate is a Universal Gate, so it can be used to construct any basic logic gate without using any other Gate. Also, it can solve complex Logical Problems.
- Simplify Logical Expressions: Using only the NAND gate, we can simplify any complex logical circuits and represent them in a simpler manner.
- Low Components Needed: NAND gate can represent any other logic gate, we can utilize NAND gates to solve complex logical expressions, and as a result, a small number of NAND gates are required.
- Less Power Consumption: Implementing logical functions using a NAND gate consumes way less power than other gates.
Disadvantages of NAND Gate
- Lack of Flexibility: Although NAND is a Universal Gate, implementing all logic circuits using a NAND gate might not always yield the most optimized result.
- Speed: In some cases using the NAND gate might result in a propagation delay, those logical expressions might need some dedicated Gates to resolve.
Frequently Asked Questions on NAND Gate – FAQ’s
Why is NAND Gate called Universal Gate?
NAND Gate is called Universal Gate because it can be used to form any other basic logic gates like AND OR NOT without taking the help of another gate.
How is a NAND gate different from an AND gate?
When we inverse the output of the AND gate we get the NAND gate. Means that the result of the AND gate will just be reversed in case of NAND gate. It is short form of NOT-AND gate.
How Logical NOT operation is achieved in NAND gate?
The logical NOT operation is performed on the output of the AND gate. The NAND gate is a combination of AND and NOT gate, where two or more input enters the AND get and yields a single output which is then fed into the NOT gate which yields the complement of the output.
Is XOR Gate is same as NAND Gate?
An XOR gate can be formed by connecting four NAND gates
Similar Reads
NAND Gate
NAND Gate is the special type of logic gate which is also known as the Universal Gate, because it can be used to implement other basic logic gates like AND, OR, and NOT. It performs NAND(NOT AND) operation between two or more binary inputs and gives output binary signal. This is a combination of AND
6 min read
NOT Gate
This article will explain the concept of NOT gate operation in digital electronics along with its truth table, logic symbol, switching circuit diagram, etc. The NOT gate is one of the main building blocks of Digital Logic Circuits. A NOT Gate, also called an inverter, has only one input and one outp
8 min read
NOR Gate
NOR gate performs NOR(NOT OR) operation between two or more binary inputs and gives output binary signal. This is a combination of OR gate and NOT gate. It gives the output high(1) only when all of its inputs are low(0). In simple words we can say that NOR gate is the opposite (inverted) of OR Gate.
6 min read
XNOR Gate
In digital electronics, the XNOR gate is a type of logic gate used to perform an exclusive NOR gate. It is a special type of logic gate used in digital circuits. An XNOR gate, also known as an equivalence gate or an EX-NOR gate, is a digital logic gate that outputs true (1) when an even number of tr
10 min read
OR Gate
OR GATE is most widely used digital logic circuit and is known as a primitive digital electronics building block in digital logic. The output state of OR gate will be high i.e.,(1) if any of the input state is high or 1, else output state will be low i.e., 0. The Boolean Expression for the OR gate i
7 min read
XOR Gate
The XOR or Exclusive OR Gate is a special type of logic gate used in digital electronics to perform the exclusive OR operation. The XOR gate takes two inputs and produces an output depending on the combination of the two inputs applied. In, this article will explain the complete theory of the XOR ga
9 min read
Universal Logic Gates
A logic gate is an active electronic component that uses one or more inputs to produce an output based on the bolean algebra each gate is designed to perform. Though there are various types of gates including AND, OR, NOT, NAND, NOR etc.. NAND and NOR gates are a little special. NAND gate and NOR ga
7 min read
AND Gate
AND gate is used to perform logical Multiplication of binary input. The Output state of the AND gate will be high(1) if both the input are high(1) ,else the output state will be low(0) if any of the input is low(0). The Boolean Expression or logic for the AND gate is the logical multiplication of in
5 min read
CMOS Logic Gate
The logic gates are the basic building blocks of all digital circuits and computers. These logic gates are implemented using transistors called MOSFETs. A MOSFET transistor is a voltage-controlled switch. The MOSFET acts as a switch and turns on or off depending on whether the voltage on it is eithe
4 min read
GATE CSE preparation story
GATE is the most prestigious post graduate exam for engineering students. Gate score is also taken by many PSU's (Public sector Undertakings) for recruitment and job offerings. PSU'S are government owned corporations offering jobs directly to top scorers of GATE exam. A good score in GATE can direct
3 min read