四,半导体存储器(续) 4.2双极型晶体管存储器由于双极型晶体管电路比MOS电路速度快,可以设想,用双极型晶体管构成的存储器会比MOS存储器速度更快。由于它的速度快,工作电平与主机相容,易于和其它部分连接,所以使用也很广泛。一、存储单元(1)普通多射极交叉耦合存储单元我们首先讨论最普通的存储单元,如图4-21所示。晶体管T_1和T_2的发射极E_2和E_4连到字选线。字选线在静态时处于最 4.2 Semiconductor Memory (Continued) 4.2 Bipolar Transistor Memory Since bipolar transistor circuits are faster than MOS circuits, it is conceivable that memories constructed with bipolar transistors will be faster than MOS memory. Because of its speed, work-level compatible with the host, easy to connect with other parts, so the use is also very extensive. First, the memory cell (1) common multi-emitter cross-coupled memory cell We first discuss the most common memory cells, as shown in Figure 4-21. The emitters E_2 and E_4 of the transistors T_1 and T_2 are connected to word select lines. Word line selection is at its most static