The above simulation example shows the implementation of a 6-input NAND gate using only 2-input NAND gates. How to design Multi- input NAND gate circuit?Ĭommercially NAND gate ICs are available with 2,3, and 4-input NAND gates but to implement more than 4-input NAND gates we should cascade lower-input NAND gates. How to design a 4-input NAND gate circuit using 2-input NAND Gate? In the same way, if more than 2,3 or 4 input NAND gate circuit is required then we should implement it with cascading of lower input gates as explained below. In the above 3-Input NAND gate simulation, if all the input bits are “HIGH” then the output is “LOW” hence LED is not glowing in that situation. We should observe in the simulation that if any input is “LOW” then the output “LED” is glowing. The truth table can be verified using the above simulation. The Boolean expression of NAND gate is given below Boolean expression of NAND gate 2-Input NAND Gate Simulation and Truth Table A (Input) The bubble shows inverted output from gate. In a simplified mode, we use NAND gate symbol as represented in the second figure. The first figure shows the NAND gate is a combination of the AND and NOT gates. In other words, it gives a complement or inverted output of AND gate. The output of the NAND logic gate is “HIGH” when all the inputs are “LOW”.The NAND gate is a combination of AND-NOT gate.OR, AND, and NOT can be implemented by only the NAND gate. The NAND gate is also called a UNIVERSAL gate in a digital electronics circuit.How to design Multi- input NAND gate circuit?.How to design a 4-input NAND gate circuit using 2-input NAND Gate?.2-Input NAND Gate Simulation and Truth Table.NAND Gate Symbol and Boolean Expression.O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers. Get Introduction to Digital Systems: Modeling, Synthesis, and Simulation Using VHDL now with the O’Reilly learning platform. The resulting truth table for this circuit is also shown in Figure 5.5, which is the same. On the other hand, if any one of the inputs or both inputs is low (i.e., logic 0), one or both transistors will be turned off and act as an open switch, and thus the output will remain high (i.e., logic 1). Consider the case when both inputs are high (i.e., logic 1) and NMOS transistors T 1 and T 2 are both turned, pulling the output node down to ground, resulting in logic 0 as output. Now observe the circuit diagram shown in Figure 5.5. The truth table is also shown in Figure 5.4.įigure 5.4 NMOS Inverter Gate and Its Truth Table 5.4.2 NMOS NAND Gate It will be replaced with a PMOS transistor in later circuit design. In other words, this resistor acts as a current source load. The purpose of resistor R is to limit the current when the NMOS transistor is turned on. The circuit in Figure 5.4 acts as an inverter gate. However, if V G = V DD (logic 1), the NMOS switch is closed and the NMOS transistor T 1 starts conducting, thereby pulling down the output node to ground. The output voltage V out is equal to V DD (logic 1). When V G = 0V (logic 0), the NMOS transistor T 1 is off and no current flows through resistor R. The operation of the circuit can be explained as follows. 5.4 NMOS AND PMOS LOGIC GATES 5.4.1 NMOS InverterĬonsider the circuit shown in Figure 5.4.
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