What is a logic gate?

A building block that gives one binary output from one or more binary inputs by a logical rule

A device that stores analog voltages

A gate that always gives the same output regardless of inputs

A circuit that works only with decimal numbers

Which gates are called universal gates, and why?

AND and OR, because they have the most inputs

XOR and XNOR, because they are used in adders

NOT and AND, because every IC contains them

2081 Baishakh (new course) · 3 marks

Short note: Logic gates

Short answer

Logic gates are digital circuit elements that perform Boolean operations on binary inputs. Basic gates include AND, OR, NOT, NAND, NOR, XOR, XNOR; NAND and NOR are universal gates. They are used in adders, counters, memories, and control circuits.

Write a short note on Logic Gates.

Logic gates are the basic building blocks of digital circuits. A gate has one or more binary inputs (0 or 1) and gives one binary output according to a logical rule. They are made from transistors and diodes in ICs (TTL, CMOS).

Gate	Expression	Output is 1 when
AND	$Y=A\cdot B$	all inputs are 1
OR	$Y=A+B$	at least one input is 1
NOT	$Y=\bar A$	the input is 0 (inverter)
NAND	$Y=\overline{A\cdot B}$	at least one input is 0
NOR	$Y=\overline{A+B}$	all inputs are 0
XOR	$Y=A\oplus B$	inputs are different
XNOR	$Y=\overline{A\oplus B}$	inputs are the same

Truth table for two-input gates:

A	B	AND	OR	NAND	NOR	XOR	XNOR
0	0	0	0	1	1	0	1
0	1	0	1	1	0	1	0
1	0	0	1	1	0	1	0
1	1	1	1	0	0	0	1

NAND and NOR are called universal gates, because any logic function can be built using only one of them. Gates are used in adders, counters, memories, alarms and control circuits.

✓ Answer checked by Claude Opus 5.5 (high effort)

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