Designed for Digital Data Transmission
Over 50-W to 500-W Coaxial Cable, Strip
Line, or Twisted Pair
High Speed
tpd = 20 ns Maximum at CL = 15 pF
TTL Compatible With Single 5-V Supply
2.4-V Output at IOH = –75 mA
Uncommitted Emitter-Follower Output
Structure for Party-Line Operation
Short-Circuit Protection
AND-OR Logic Configuration
Designed for Use With Triple Line
Receivers SN55122, SN75122
Designed to Be Interchangeable With
Signetics N8T13

description
The SN55121 and SN75121 dual line drivers are
designed for digital data transmission over lines
having impedances from 50 to 500 W. They are
also compatible with standard TTL logic and
supply-voltage levels.
The low-impedance emitter-follower outputs of
the SN55121 and SN75121 can drive terminated
lines such as coaxial cable or twisted pair. Having
the outputs uncommitted allows wired-OR logic to
be performed in party-line applications. Output
short-circuit protection is provided by an internal
clamping network that turns on when the output
voltage drops below approximately 1.5 V. All of the
inputs are in conventional TTL configuration and
the gating can be used during power-up and
power-down sequences to ensure that no noise is
introduced to the line.
The SN55121 is characterized for operation over
the full military temperature range of –55°C to
125°C. The SN75121 is characterized for
operation from 0°C to 70°C.