NOR gate

from Wikipedia, the free encyclopedia
Gate types

A NOR gate (from English : n ot or - not or , or from English nor - (neither -) nor; also called Peirce function after Charles S. Peirce ) is a logic gate with two or more inputs A, B, ... and an output Y, between which there is a logical NOT OR link . A NOR gate outputs 1 (w) when all inputs are 0 (f). In all other cases, i. H. if at least one input is 1, a 0 is output.

The literature uses the following notations for the NOR operation of variables A and B :


function Circuit symbol Truth table Relay logic
IEC 60617-12 US ANSI 91-1984 DIN 40700 (before 1976)

IEC NOR label.svg
A. B. Y = A ⊽ B
0 0 1
0 1 0
1 0 0
1 1 0
Relay nor.svg


The electronic implementation takes place, for example (with positive logic ) with two (or correspondingly more) switches ( transistors ) connected in parallel , which connect output Q to ground (logic 0) as soon as one of them is switched on. If all are off, the ground connection is interrupted and the output Q is at positive potential (logical 1).

Logic synthesis

According to the following logical equivalence , a NOR operation can also be built up from NAND gates alone :

Logical links and their implementation using NOR gates:

With the Peirce function alone, all two-valued truth functions can be represented, i.e. every Boolean function is equivalent to a formula that only contains the NOR function. Because of this property of functional completeness , the peirce function is called a basis of the two-digit logical functions (another basis is the NAND function).

NOT ( negation , not)
AND ( conjunction , and)
NAND (not-and)
OR ( disjunction , or)
NOR (not-or)
XOR (Exclusive-Or)
XNOR (Exclusive-Not-Or)
Verum (always true)
Falsum (always wrong)


  • Ulrich Tietze, Christoph Schenk: Semiconductor circuit technology . 12th edition. Springer, 2002, ISBN 3-540-42849-6 .