4001 CMOS Quad-2-input NOR Gate Chip Pinouts
This blog post shows the truth table for a 2 input NOR gate and the pinouts of the common 4001 CMOS quad 2 input NOR gate chip.
With thanks to Anthony McCloskey, from the raspberry-vi mailing list for the suggestion of this post and the pinouts.
What is a NOR Gate?
NOR is a way of saying ‘not or’.
This chip contains four NOR gates, each of which have two inputs and an output.
We can show the relative states of each of the pair of inputs of a single gate, and the resulting state of the output.
In the truth table below, the inputs are labelled A and B, and Q is the output:
| A | B | Q |
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
Boolean Expression Q = A+B
Read as A OR B gives NOT Q
Or, if any of the inputs is high, then Q will be low. Only in the case where both inputs are low, will Q be high.
Here is the table showing the function of each ot the fourteen pins:
| Pin | Function |
|---|---|
| 1 | Gate 1 input 1 |
| 2 | Gate 1 input 2 |
| 3 | Gate 1 output |
| 4 | Gate 2 output |
| 5 | Gate 2 input 1 |
| 6 | Gate 2 input 2 |
| 7 | GND |
| 8 | Gate 3 input 1 |
| 9 | Gate 3 input 2 |
| 10 | Gate 3 output |
| 11 | Gate 4 output |
| 12 | Gate 4 input 1 |
| 13 | Gate 4 input 2 |
| 14 | Vcc |