3-input AND gates

bst_14.gif (721 bytes)

Technology: CMOS Power supply: 3-15 V

14-pin DIL


Pin connections Basic operation
Truth table LINKS . . .

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Pin connections

4073 pin connections The 4073 has three separate 3-input AND
gates which you can use independently.


Truth table

The truth table of each individual gate is:

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

where '0' represents a LOW voltage, and '1' represents a HIGH voltage.


Basic operation

You can investigate the behaviour of a single 3-input AND gate using this circuit:

4073 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 4073 to +9 V and pin 7 to 0 V.

This is the test circuit built on prototype board:

4073 3-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.



Cross references in the Beastie Zone:

AND gate

4081 quad 2-input AND gate, 4082 dual 4-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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