UNDERSTANDING NAND GATE (CD4011)

UNDERSTANDING NAND GATE (CD4011)

INTRODUCTION
CD4011 is the most commonly used Complementary Metal Oxide Semiconductor (CMOS) chip.  It comes in a 14 pin Dual Inline Package (DIP). It has small notch on one side which identifies as pin 1.It consists of 4 independent NAND gate in a single chip. Each gate has 2 inputs and 1 output. Working voltage range of IC is from 5V to 16V. It can deliver approx.10mA at 12V but this can be reduce as power supply voltage reduces.
IC consist of 14 pin in this pin 7 and 14 is connected to battery or DC power supply. Negative is connected to pin 7 and pin 14 is connected to power supply. As we know it has four gates we call it NI1, NI2, NI3, NI4. In first gate NI1 pin 1 and 2 are for inputs and pin 3 is for output. As you can see in the circuit below.
As we can see in the truth table it will provide the output equal to one when any one of the input is low. In another words we will receive the high output when any of the signals goes low. And if both the inputs are high we will receive the low output.

Working of NAND Gate
To understand the working let us consider a circuit diagram of gates
In the diagram above consider that we have supply logic high to pin1 and 2 of NI1as a result we will receive logic 0 in output pin 3 as you can see in truth table. Therefore we will  receive logic 1 at output of pin 4 because 0 is passed to NI2 gate from pin3 so whatever may be the input from pin 6 we will receive high at pin 4. This means that we will receive 12 V at pin 4. As a result current start following in capacitor and capacitor starts to charging as a result we will receive high on pin 8 and 9 and logic 0 at pin 10 because of which it is connected to pin 6.As a result we will not require pin 5 output is maintained by gate NI2 and NI3.
But as capacitor charges voltage on resistor drops to half the power supply NI3 detects a low on in its input as a result logic 0 appear on pin 10. Now logic 1 is on pin 5 because no logic is present on pin 1 and 2 as pin 6 is also high we will receive 0 at pin 4 as result capacitor start discharging on pin 8 and 9 and circuit again start working.
From above we can see that for a certain period of time circuit will work and then goes off. Time period of operation can be determine by-T=.7*R*C.

Application Of NAND Gate
Logic gate have many application like in computer circuits.

1. The circuit below show how a NAND gate is used to activate a light bulb if any of the door is left open. A door which is properly shut will open a normally closed pushbutton switch and apply a logic “1”to the gate input as a result bulb will not glow and when any of the door is not properly shut applies a logic “0” to the gate and a result bulb will glow and we came to know that any of the door is not properly shut.

2. NAND  Gate as INVETER-

   IN	OUT
   L	H
   H	L

   
   
   In the circuit diagram above when we will give input equal to 1 we will receive output as 0 and when 0 is given we will receive 1 as output.
   
   3. NAND Gate as Switch
   The circuit below will give a high output when we touch the both wire together. Working of the circuit is very simple as pin 2 is connected to power supply it is always maintained a high at its input. When wires are not touch circuit is open and we receive a high at pin 1 and when wires are touch we will receive 0 at pin 1 and we will get the output as a result LED will glow.