TTL logic is typically a totem pole type structure. It's actively driven in both directions.
The open collector inverter has somewhat been depreciated because of devices like the ULN2003. Recently there was a similar device that was introduced that works at lower logic voltages.
Sink current is usually high with an OC inverter, so lamp LED driving was a typical use. You can convert an OC nverter to an inverter with a pull up resistor, but FAN out might be affected.
FAN out is a term used to describe the # of inputs an output can drive.
There is a lot more than meets the eye and some manufactures have a "logic family" description. It makes sense to understand that document first for it defines what is a logic high and what is a logic low. Now, it's usually described as a percentage of Vcc because Vcc can vary. CMOS puts high and low really really close to the supply rails making interfacing logic families hard.
The "pull up" structure is used a lot with switches, so an OC inverter can effectively create an OR to a switch input. Multiple OC devices can be placed in parallel to get an effective OR gate.
You have to get your head around, that a high on the input of an OC gate causes a low on the output and might turn on a LED or activate a switch.
One BIG advantage of the ULN2003 type devices is interfacing, It will tolerate an input that is open. An open state is OFF. A logic one is ON. On the other hand, if an OC inverter is used for the same interfacing, if you disconnect the (interface), the stuff that it's connected to, turns on because of the inputs of the OC inverter float high.
This is also a practical reason why NOT ENABLE is used on motor drivers.
Another advantage of the ULN2003 type devices in microprocessor interfacing. Many ports were defined as inputs at power up and when these are inputs, they won;t affect the state of a relay when the port is changed to an output.
The TI DRV777
https://www.google.com/url?sa=t&rct...wzSwMepntZieU7w&bvm=bv.70138588,d.aWw&cad=rja is a new generation driver similar to the ULN2003.