What the SN74145N is and where it fits
The SN74145N is a 7400-series TTL decoder that takes a 4-bit BCD input and drives one of ten active-low outputs low. It is a single-supply device operating from 4.75 V to 5.25 V, in a 16-pin DIP package for through-hole assembly. The commercial temperature range (0°C to 70°C) suits it for indoor equipment such as test instruments, industrial controllers, and office peripherals where a 5 V logic rail is available.
80 mA sink — what that means for the load
The output is rated for 80 mA low-level current (sinking), with no specified high-level source current. That means this decoder is designed to drive loads referenced to ground — relays, LED anodes, or logic inputs — by pulling them low. The 80 mA per output is enough to drive a small relay coil or a bank of LEDs directly, but the total package dissipation and supply current need checking if multiple outputs are on simultaneously.