From WikiChip
Manufacturer Prefix

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
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