SN7400N - The company prefix SN indicates this is a Texas Instruments manufactured part. This can also be confirmed through the TI logo.

Manufacturer Prefix or IC Company Prefix or ID are identification codes various semiconductor companies use to identify their integrated circuits. Those IDs are usually found as the first few letters of the part number. They may often be found on the IC package itself as well along with a possible logo.

Prefix	Company	Note
AD	Analog Devices
AM	Advanced Micro Devices
AT	Atmel
BQ	Benchmarq Microelectronics
CA	RCA	Analog devices
CD	RCA	Digital devices
DM	Fairchild
DM	National Semiconductor
DS	Dallas Semiconductor (now Maxim Integrated)
EP	Altera	Normal series
EPC	Altera	EPROMs
EPF	Altera	Flex series
EPM	Altera	MAX Series
HA	Hitachi	Analog devices
HD	Hitachi	Digital devices
LM	National Semiconductor
MA	TESLA
MAA	TESLA
MC	Motorola
MH	TESLA
MHB	TESLA
MM	Monolithic Memories
MM	National Semiconductor
N	Signetics
NE	Signetics
PC	Signetics
RC	Ratheon
RM	Ratheon
SE	Signetics
SN	Texas Instruments
TI	Texas Instruments
UA	Fairchild
μA	Fairchild
XC	Xilinx
Z	Zilog