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SN74LS27N

Triple 3-input NOR gate, LS TTL, 12ns, PDIP-14

4000

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Pieza del fabricante：

SN74LS27N

Paquete：

PDIP-14 (19.3 x 6.35 x 4.57mm, 2.54mm pitch, through-hole)

Marca：

Categorías de productos：

Circuitos integrados IC, Circuitos integrados de interfaz

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Descripción

Productos

The SN74LS27N from Texas Instruments contains three independent 3-input positive NOR gates in a 14-pin PDIP package — ideal for multi-input OR logic with active-LOW output.

Especificaciones

Number of Gates	3 (triple 3-input NOR)
Logic Family	LS (Low-power Schottky)
Tensión de alimentación	4.75V to 5.25V
Retardo de propagación	12ns typical @ 5V
Output Drive (IOL/IOH)	8mA / -0.4mA
Temperatura de funcionamiento	0°C to +70°C
Paquete	PDIP-14 (19.3 x 6.35mm)

Características

Triple 3-input NOR gates
LS TTL technology
12ns typical propagation delay
Three gates in one 14-pin package

Aplicaciones

3-input OR function (NOR + inverter)
Active-LOW detection (any input HIGH → output LOW)
Multi-condition alarm
General-purpose logic

Introducción del producto:SN74LS27N Presentación del producto

The SN74LS27N from Texas Instruments contains three independent 3-input NOR gates in a 14-pin PDIP package. Each gate performs Y = NOT(A OR B OR C); the output is HIGH only when ALL three inputs are LOW. The NOR gate is the complement of the OR gate, and by DeMorgan’s theorem, NOR is also equivalent to NOT-A AND NOT-B AND NOT-C. The 7427 is useful for detecting when none of three conditions is active (all LOW → output HIGH), or for implementing 3-input OR logic by adding an inverter. The three gates in one package provide more logic density than using three 2-input NOR gates (7402) to implement 3-input functions. The N suffix denotes the PDIP-14 through-hole package.

Principio de funcionamiento:SN74LS27N Principio de funcionamiento

Each 3-input NOR gate in the SN74LS27N performs Y = (A + B + C)’ — the output is HIGH only when all three inputs are LOW simultaneously. If ANY input is HIGH, the output goes LOW. Truth table: 8 possible input combinations, only one (000) produces HIGH output. By DeMorgan’s theorem: (A + B + C)’ = A’ · B’ · C’ — the NOR output is HIGH when A is LOW AND B is LOW AND C is LOW. For a 3-input OR function: Y = A + B + C — add an inverter after the NOR, or use the NOR with DeMorgan’s equivalent. For active-HIGH alarm detection: connect three fault signals to the NOR inputs; when any fault goes HIGH, the NOR output goes LOW (active-LOW alarm). For active-HIGH alarm: add inverter. Three 3-input NOR gates can implement moderately complex combinational logic in a single 14-pin IC.

Descripción de la clavija:SN74LS27N Definición y funciones de las clavijas

Pin	Nombre	Tipo	Descripción
1	1A	Entrada	Gate 1 input A
2	1B	Entrada	Gate 1 input B
3	2A	Entrada	Gate 2 input A
4	2B	Entrada	Gate 2 input B
5	2C	Entrada	Gate 2 input C
6	2Y	Salida	Gate 2 output (NOR)
7	GND	Potencia	Suelo
8	3Y	Salida	Gate 3 output (NOR)
9	3A	Entrada	Gate 3 input A
10	3B	Entrada	Gate 3 input B
11	3C	Entrada	Gate 3 input C
12	1C	Entrada	Gate 1 input C
13	1Y	Salida	Gate 1 output (NOR)
14	VCC	Potencia	Supply (5V)

Application Scenarios:In which products and applications isSN74LS27N usado

3-Input OR: 3 signals → 7427 NOR → 7404 inverter → active-HIGH OR output
All-Clear Detect: 3 status signals → NOR; output HIGH only when all 3 are LOW (all-clear)
Active-LOW Alarm: Overtemp, Overvoltage, Overcurrent → NOR; output LOW when any fault is HIGH
Sum-of-Products: Combine NOR gates with inverters to implement product-of-sums logic forms

Alternative Models:What chips are recommended as replacements for SN74LS27N

Modelo	Fabricante	Diferencia clave	Paquete	Supply
74LS27N	TI/Nexperia	Original TTL version with 5V-only supply, typical propagation delay 10-15ns	DIP-14	5V TTL
74LS27D	TI/Nexperia	Surface-mount SOIC version of LS with identical logic function	SOIC-14	5V TTL
74HC27D	TI/Nexperia	CMOS version with wide 2-6V supply range, lower power consumption and higher noise immunity	SOIC-14	2-6V CMOS
74HC27N	TI/Nexperia	Through-hole DIP version of HC family for prototyping and repair	DIP-14	2-6V CMOS
74HCT27D	TI/Nexperia	CMOS with TTL-compatible input levels, ideal for mixing with LS devices at 5V	SOIC-14	4.5-5.5V TTL-in
74HCT27N	TI/Nexperia	Through-hole DIP version of HCT family for prototyping and repair	DIP-14	4.5-5.5V TTL-in
74AC27D	TI/Nexperia	Advanced CMOS with 2-6V supply and higher output drive current (24mA vs 6mA for HC)	SOIC-14	2-6V CMOS
74AC27N	TI/Nexperia	Through-hole DIP version of AC family for prototyping and repair	DIP-14	2-6V CMOS

The 7427 is a Triple 3-Input NOR Gate. Family variants span from the original LS TTL (5V only) to modern LVC/AUP (down to 0.8V). HC and HCT versions offer 2-6V CMOS operation with HCT providing TTL-compatible input thresholds for mixed 5V systems. CD4000-series equivalents offer the widest 3-18V supply range at the cost of lower switching speed. DIP packages (N suffix) are through-hole; SOIC (D suffix) and TSSOP are surface-mount.