说明：  清华大学和浙江大学电子设计学习资源网站，与大家共享，讲得很好很细致！另附TTL与CMOS的区别，很详细！
(Tsinghua University and Zhejiang University e-learning resources web site design, and share, put it very very carefully! The difference between TTL and CMOS attached, very detailed!)