无意间发现一个很好的学习网站，是关于电子，电路方面的：
All About Circuits
http://www.allaboutcircuits.com/
分了很多不同章节的内容：
- Volume I – DC Basic Concepts of Electricity, OHM’s Law, Electrical Safety, Scientific Notation…
- Volume II – AC Basic AC Theory, Complex Numbers, Reactance and Impedance, Resonance…
- Volume III – Semiconductors Amplifiers and Active Devices, Solid-State Device Theory, Diodes and Rectifiers…
- Volume IV – Digital Numeration Systems, Binary Arithmetic, Logic Gates, Switches…
- Volume V – Reference Conversion Factors, Resistor Color Codes, Math References, Periodic Table…
- Volume VI – Experiments Test Equipment, DC Circuits, AC Circuits, Discrete Semiconductor Circuits…
甚至还有视频学习内容：
和论坛，及博客：
值得一看。