Coisas Flashcards
Corrente de saturação why???
Zener breakdown
Avalanche
Zener
Zener breakdown is observed in
highly doped p-n junctions and
occurs for voltages of about 5 V or
less. The conduction and valance
bands on opposite side of the
junction become so close during the
reverse-bias that the electrons on
the p-side can tunnel directly from
VB into the CB on the n-side.
avalanche
Avalanche breakdown is observed in less doped p-n junctions. This mechanism occurs when electrons and holes move through the DR and acquire sufficient energy from the electric field to break a bond i.e. create electron-hole pairs by
colliding with atomic electrons within the
depletion region. The newly created electrons and holes move in opposite directions due to the electric field and thereby add to the existing reverse bias current
Capacidade depleção
– When a reverse bias is applied to p-n junction diode, the depletion region width, W, increases. This cause an increase in the number of the uncovered space charge in depletion region.
– Whereas when a forward bias is applied depletion region width of the p-n junction diode decreases so the amount of the uncovered space charge decreases as well.
– So the p-n junction diode behaves as a device in which the amount of charge in depletion region depends on the voltage across the device. So, it looks like a capacitor with a variable capacitance.
Junções de schotcky
Contactos ohmicos: metal com semicondutor muito dopado
Diodos de schottky: metal com semicondutor pouco dopado
Função de trabalho
invariante no metal
Dependente da dopagem nos semicondutores
Aplicações Diodo de schottky
->I0 of a Schottky diode is 103
to 108 times larger than a PN junction diode
majority- vs minority-carrier current), depending on B
. Larger I0 means a
smaller forward drop V.
– This lower voltage drop can provide higher switching speed and better system
efficiency.
– A Schottky diode is the preferred rectifier in low voltage, high current
applications
