CD4001 (CD4001B): the quad 2-input NOR gate chip, live

The CD4001 is a 4000-series CMOS chip with four 2-input NOR gates: J = NOT (A OR B), K = NOT (C OR D), L = NOT (E OR F) and M = NOT (G OR H). It runs from 3 V to 18 V and shares its pinout with the CD4011, not the 7402. This live chip has all four gates.

TI's datasheet (from Harris Semiconductor) lists the CD4001B with the dual 4-input CD4002B and the triple 3-input CD4025B as NOR gates that "provide the system designer with direct implementation of the NOR function", with all inputs and outputs buffered, for supplies from 3 V to 18 V. Its pinout is the 4000-series quad layout: the same pins as the CD4011 NAND and the CD4081 AND, with two outputs side by side on pins 3 and 4 and on pins 10 and 11. The TTL-family 7402 does the same logic with its outputs on pins 1, 4, 10 and 13, so the two are not interchangeable. NOR is a universal gate (see NOT, OR and AND from NOR), and two NOR gates cross-coupled, each output feeding one input of the other, make the SR latch, which is why a CD4001 turns up in so many simple set and reset circuits. Each gate here is the CMOS NOR. All 256 combinations of the eight inputs are checked before the page is built.

Live circuit: click the inputs to toggle them and watch the outputs update. It runs the real simulator, right here on the page.

Open this circuit in the lab →

What you need

4× 2-input NOR: J from A, B; K from C, D; L from E, F; M from G, H

Step by step

Power the chip: VDD on pin 14 and VSS on pin 7, anywhere from 3 V to 18 V.
Each gate has two inputs and one output; find their pins in the pinout below.
Tie every unused input to VCC or GND: a floating CMOS input can drift and draw current.
Set both inputs of one gate to 0: its output goes to 1. A 1 on either input gives 0.

CD4001 pinout

Pin	Name	Pin	Name
1	A	14	VDD
2	B	13	H
3	J	12	G
4	K	11	M
5	C	10	L
6	D	9	F
7	VSS	8	E

2-input NOR truth table (each gate)

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	0

Pin numbers and names are from TI's CD4001B (SCHS015C) datasheet, checked 2026-10-25. Each gate is independent; the chip only shares the power pins.

You can also read the full theory in the lesson on the NOR gate. Prefer to build it yourself from scratch? Open the digiwleea lab and place the gates on the canvas, or start from the logic gate simulator.

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Each of these is one step from a transistor to a working CPU. Build every gate from CMOS transistors and work all the way up in the free digiwleea lab, with the free theory reference alongside.

Open the CD4001 quad 2-input NOR chip in the lab →

Frequently asked

What is the CD4001?

A 4000-series CMOS chip with four 2-input NOR gates, for supplies from 3 V to 18 V. Each output is HIGH only when both of its inputs are LOW.

What is the CD4001 pinout?

Pin 1 A, 2 B, 3 J, 4 K, 5 C, 6 D, 7 VSS, 8 E, 9 F, 10 L, 11 M, 12 G, 13 H, 14 VDD, with J = NOT (A OR B), K = NOT (C OR D), L = NOT (E OR F) and M = NOT (G OR H).

Is the CD4001 the same as the 7402?

Same logic, different pinout and supply range. Both have four 2-input NOR gates, but the CD4001's outputs are on pins 3, 4, 10 and 11 and the 7402's on 1, 4, 10 and 13. The CD4001 runs from 3 V to 18 V.

How do you make an SR latch with a CD4001?

Use two of its gates: connect each gate's output to one input of the other. The two free inputs are S and R, both active HIGH, and the two outputs are Q and Q'. Keep S and R low to hold the stored bit.