Electronic schematic of 7408 and 7432 logic IC
How are these schematics different from the traditional BJT logic gates that we learn in high school? 


More detail will help us answer better but, typical BJT based gates probably use "Diode-Transistor Logic" as used in early DTL gates. In this system multiple diodes are used as inputs to allow input signals to influence the BJT without interacting with the other inputs.

TTL and later gates tend to use input transistors with multiple emitters - one per input. However, an example of a DTL gate lurking inside a TTL type "LS TTL" gate can be seen in the middle diagram below. While the left hand TTL example and the right hand STTL (Schottky TTL) use multiple emitters as inputs, the LSTTL (low power Schottky TTL) uses 2 diodes to the base of an internal BJT.

See data sheet, page 2 for larger version.

The LSTTL gate is essentially a "DTL gate" with a single transistor at the input and two diodes and a resistor used to perform the logic function.

The TTL and STTL gates use multiple emitters on the input transistor to achieve multiple inputs. None of the BJT's available in high-school had multiple emitters. The dioes here serve the same function.   





You can get an approximation to an N emitter transistor by using N BJTs, joining all the N bases, joining all the N collectors and using the N emitters in the same way as the multiple emitters on the multiple-emitter transistor.