3-input NOR gates
+ inverter

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

4000 pin connections

The 4000 has two separate 3-input NOR
gates and a single NOT gate, or inverter.

NC = no connection


Truth table

The truth table of each 3-input NOR gate is:
input C input B input A output
0 0 0 1
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 0
The truth table of the NOT gate is:
input A output
0 1
1 0

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


Basic operation

You can investigate the behaviour of one of the 3-input NOR gates using this circuit:

4000 3-input NOR gate 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 4000 to +9 V and pin 7 to 0 V.

This is the test circuit built on prototype board:

click for pins! 4000
4000 3-input NOR 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: 4001, 2-input NOR, 4002 4-input NOR, 4025 3-input NOR, 4078 8-input NOR

Cross references in Design Electronics:

External links:

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