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4002B Dual 4-input NOR gates 
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 1. Pin connections |
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| 2. Truth table |
 DDE2 : Logic Gates |
| 3. Basic operation |
DDE3 : Astables  |
| 4. Links |
DDE4 : Monostables |
| Bookshelf |
4060 counter/divider |
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1. Pin connections
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2. Truth table
The truth table of each individual gate is:
| input D | input C | input B | input A | output |
| 0 | 0 | 0 | 0 | 1 |
| 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 | 0 |
| NOR gate truth table |
where '0' represents a LOW voltage, and '1' represents a HIGH voltage. Shading is intended to make the table easier to follow.
3. Basic operation.
You can investigate the behaviour of one of the 4-input NOR gates using this circuit:
| 4-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 µF or 100 µF, across the power supply. (This helps to prevent the transfer of spikes along the power supply rails.)
- Beasties need power supplies! Don't forget to connect pin 14 of the 4002 to +9 V and pin 7 to 0 V.
Here is the circuit on prototype board:
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  4002B NOR gate test circuit |
In the prototype circuit, it is not essential to make connections to the unused gate. 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.
4. Links
Excellent
reference book..
4.1 Data sheets
The links below allow you to download documents in 
Adobe Acrobat ©, PDF, format. In the unlikely event that you don't already have Acrobat Reader, you can download the latest version direct from Adobe:
4002B data sheet (Philips Semiconductors, 1995)
4002B data sheet (ST Microelectronics, 2004)
4.2 DOCTRONICS links
4001 2-input NOR
4025 3-input NOR
4078 8-input NOR
