Multiple base/emitter transistors

[Kevin Weddle]

A biploar transistor OR gate uses an input transistor with two emiiters. I have never seen these used elsewhere and am surprised to see it used for OR gate design. Are unusual devices not seen so much because of cost, availability, or design difficulty?

 

[praveenkv1988]

Those components are not available for external usage. The ckt. you are referring is an implementation of OR gate. (How it is implemented inside an IC).