Especially, the circuit of NAND gate my be totally made by NPN transistor, and the circuit structure is simple, easily is complicated by Integrate circuit.
其与非门电路不仅全部由npn型晶体管构成，且结构非常简单，容易做成集成电路。
2
The SR Flip-Flop is a circuit with two cross-coupled NOR gates or two cross-coupled NAND gates.