4082

4-input AND gates

bst_14.gif (721 bytes)


Technology: CMOS Power supply: 3-15 V

14-pin DIL


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Pin connections Basic operation
Truth table LINKS . . .

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Pin connections

4082 pin connections The 4082 has two separate 4-input AND
gates which you can use independently.
(NC=no connection)

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Truth table

The truth table of each individual 4-input AND gate is:

input D input C input B input A output
0 0 0 0 0
0 0 0 1 0
0 0 1 0 0
0 0 1 1 0
0 1 0 0 0
0 1 0 1 0
0 1 1 0 0
0 1 1 1 0
1 0 0 0 0
1 0 0 1 0
1 0 1 0 0
1 0 1 1 0
1 1 0 0 0
1 1 0 1 0
1 1 1 0 0
1 1 1 1 1

where '0' represents a LOW voltage, and '1' represents a HIGH voltage. As you can see, the output becomes HIGH only when all four inputs are HIGH.

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Basic operation

You can investigate the behaviour of one of the 4-input AND gates using this circuit:

4082 test circuit

The inputs of the gate must be connected, either to LOW or to HIGH, and must not be left open circuit. This is the function of the input switches with their pull-down resistors. To avoid loading the output of the gate, a transistor switch indicator circuit should be used. It is good practice with CMOS circuits to insert a decoupling capacitor, 47 F or 100 F, across the power supply. (This helps to prevent the transfer of spikes along the power supply rails.)

Don't forget - - Connect pin 14 of the 4082 to +9 V and pin 7 to 0 V.

This is the test circuit built on prototype board:

4082 4-input AND gate test circuit

In the prototype circuit, it is not essential to make connections to the unused gates. However, in any final circuit, all unused CMOS inputs must be connected either to HIGH or to LOW. Make it an absolute rule that CMOS inputs are never left open circuit.

There is no problem with CMOS outputs. Worry about the inputs and leave any unused outputs unconnected.

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LINKS

Cross references in the Beastie Zone:

AND gate

4081 quad 2-input AND gate, 4073 triple 3-input AND gate

74LS08 quad 2-input AND gate, 74LS11 triple 3-input AND gate

74HC08 quad 2-input AND gate


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