EE 3950 Lecture : Lecture1 1
Document Summary
Conductors very little voltage is sufficient (even a few mv) Semiconductors moderately low voltages (example: cmos circuits ~ 5v, ttl ~ 3. 7v) Insulators high voltage results in electrical breakdown (example: arcing, lightning, etc) Current definition i = dq dt amount of charge carried per unit time. We need charge carriers (electrons, holes, or both) Metallurgical bond of 2 types of materials (p- and n-) D-doped holes try to diffuse electrons try to diffuse e- diffuses and leaves behind a positive ion. No built-in field is generated e- and h+ that try to diffuse get pulled back. E h+ diffuses and leaves a negative ion depletion region. P-n junction diode biasing: forward bias external field cancels built-in field. Vd is used for extra carrier injection ( spill-over ) Extra carriers neutralize ions external field: reverse bias depletion region vanishes. V-i characteristics of a p-n junction diode (cont"d)
