Apparently I misunderstood.
When you stated "there aren't any anymore" was the answer the professor was looking for, I thought you meant that TTL devices with an open collector output were no longer available.

My fault for not being obscure clearly!

 

A more correct to say: TTL gate with open collector output. Just knowing it is "open" collector. "Open" means naked, nothing further for him not to join.

 

That doesn't illustrate the advantages of the OC TTL device.

 

what are the advantages of open collector TTL

Normally TTL outputs are either actively pulled high or low. Open Collector outputs omit the high side driver, allowing multiple outputs to be tied together. Open collector outputs are also used to drive outputs at a higher voltage than VCC to drive relays, and such.
Look at data sheets for 7405 (OC, but VCC voltages), 7406, 7407, 7416, 7417.

 

Normally TTL outputs are either actively pulled high or low. Open Collector outputs omit the high side driver, allowing multiple outputs to be tied together. Open collector outputs are also used to drive outputs at a higher voltage than VCC to drive relays, and such.
Look at data sheets for 7405 (OC, but VCC voltages), 7406, 7407, 7416, 7417.

thanks @hp1729

 

Yep, between hp1729 and myself, we are doing all this guy's homework for him.

 

Well, both of you deserve a gold star.

Do you think md yasir will mention you two when he turns his work in?

 

Well, both of you deserve a gold star.

Do you think md yasir will mention you two when he turns his work in?

Why, of course! I'm absolutely positive that he won't submit our answers and claim them as his own. I mean, do people really DO that????

 

I'm breathless in anticipation of the next deep and intellectually challenging question.

 

In 1970 they may have had advantages over the competitive products which were RTL and DTL, but now maybe not so much.

With open collector, you can add a common base (or gate) output stage to make it a casc_c_ode - then the voltage limit is that of the added transistor (MOSFET).

This arrangement was used on the TTL video output on the Atari monitor to directly drive the CRT cathode.

OC outputs are usually rated 15 or 30V, so lamps or relays etc can be tied to a higher voltage than Vcc.

 

thanks @hp1729

With open collector, you can add a common base (or gate) output stage to make it a casc_c_ode - then the voltage limit is that of the added transistor (MOSFET).

This arrangement was used on the TTL video output on the Atari monitor to directly drive the CRT cathode.

OC outputs are usually rated 15 or 30V, so lamps or relays etc can be tied to a higher voltage than Vcc.

:-0

 

:-0

Yet another example of where open collector devices may be used. The pulse stretcher. It may also be used as a remote reset for an embedded microprocessor.

 

Yep, I got tricked on this one. Lost sight of the original question.

For ONCE, I didn't, and kept my keyboard shut. Now if I could just notice when a thread is 5 years old...

ak