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# NAND gate

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Introduction to Universal gate-NAND Gate

Publié dans : Ingénierie
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### NAND gate

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2. 2. DTL – DIODE TRANSISTOR LOGIC NAND GATE O NAND gate is a electronic circuit which has two or more inputs but only one output. O The NAND gate is the natural implementation for the simplest and fastest electronic circuits O The output is HIGH if at least one of its input is LOW. O The output is LOW only when all the inputs are HIGH. O The term NAND is a contraction of NOT-AND. O The NAND gate is a combination of an AND gate followed by NOT gate. 2
3. 3. 3 NAND GATE O The basic NAND gate has the following symbol and truth table: O AND-Invert (NAND) Symbol: O NAND represents NOT AND. The small “bubble” circle represents the invert function O The NAND gate is implemented efficiently in CMOS technology in terms of chip area and speed. X Y X · Y X Y NAND 0 0 1 1 0 1 0 1 1 1 1 0
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5. 5. COMPONENTS USED 5 RESISTOR DIODE (1n4002) TRANSISTOR(BC107)
6. 6. 6 O BREADBOARD O WIRES
7. 7. WORKING O Case 1 :- When both the input A and B are LOW (0V), both diodes D1 and D2 are forward biased. Therefore the voltage at the junction P of the diodes becomes zero. This drives the transistor Q to cut-off. As a result the output becomes HIGH(+Vcc). O Case 2 : - When the input A is LOW and B is HIGH, the diode D1 is forward biased whereas diode D2 is reverse biased. Therefore the voltage at the junction P of the diodes becomes zero. This drives the transistor Q to cut-off. As a result the output becomes HIGH(+Vcc). 7
8. 8. O Case 3 :- When the input A is HIGH and B is LOW, the diode D2 is forward biased whereas diode D1 is reverse biased. Therefore the voltage at the junction P becomes zero. This drives the transistor Q to cut-off. As a result the output becomes HIGH (+Vcc). O Case 4 :- When both the input A and B are HIGH, both diodes D1 and D2 are reverse biased. Therefore the voltage at the junction P becomes (+Vcc). This large voltage drives the transistor Q to saturation. The transistor acts as a closed circuit. As a result the output becomes LOW. 7
9. 9. NAND GATE AS A UNIVERSAL GATE 9
10. 10. NAND GATE AS A NOT GATES O NOT gate can be made from a NAND gate by joining all the inputs to form a single input as shown below. 10 INPUT OUTPUT 0 1 1 0
11. 11. 11 NAND GATE AS AN AND GATE X Y Z 0 0 0 0 1 0 1 0 0 1 1 1 X Y YXYXZ  YX NAND Gate Inverter Equivalent to AND Gate
12. 12. 12 NAND GATE AS AN OR GATE X Y Z 0 0 0 0 1 1 1 0 1 1 1 1 Equivalent to OR Gate X Y YXYXYXZ  X NAND GateInverters Y
13. 13. 13 ONAND gates can implement any Boolean function. ONAND gates can be used as inverters, or to implement AND / OR operations. OA NAND gate with one input is an inverter. O The NAND gate is implemented efficiently in CMOS technology in terms of chip area and speed. APPLICATIONS
14. 14. PIN DIAGRAM OF IC 7400 14