这几个都是CMOS集成电路的**Vth阈值电压**相关的基本概念。通常将传输特性曲线中输出电压随输入电压改变而急剧变化转折区的中点对应的输入电压称为**阈值电压**。 * **HVT** = High V threshold. Can be used in the path where timing is not critical. So by using HVT cells we can save power. * **LVT** - Low V threshold. One should use these cells in timing critical paths. These cells are fast but , comsumes more power due to its leakage. So it will consume more power. So use only when timing is critical. * **SVT**- Standard V threshold. Best of both world. Medium delay and medium power requirment. So if timing is not met by small magin with HVT, you should try with SVT. And at last LVT. * **RVT**- Regular V threshold.  Another name for SVT. 阈值电压越低，因为饱和电流变小，所以速度性能越高；但是因为漏电流会变大，因此功耗会变差。 速度大小按快到慢依次排列为SLVT, LVT, RVT, HVT。 功耗大小却正好相反。即HVT的cell其阈值电压最大其掺杂浓度越高，其泄露功耗最小； 对于NPN的晶体管是n型半导体，其导电是电子，P衬底多子是空穴，掺杂越高电子越少，越难以导电，阈值电压上升，泄露功耗变少。 对于PNP晶体管是P型半导体，其导电是空穴，N型衬底是电子，掺杂越高空穴越少，越难以导电。