Week 3 Flashcards
What are the two main categories used in all electronic circuits and systems?
Passive and active
What are passive components?
Passive components are those that only absorb energy. eg.,
resistors, capacitors, inductors
What are active components?
Active components are those that may deliver energy. eg.,
power supplies, batteries and also diodes and transistors
What are insulators?
Atoms with 6 or more valence electrons bond tightly. Normally few
electrons can escape from this bond providing no carrier for electric
current. These materials are called insulators (glass, wood etc.)
What are metals?
Atoms with 3 or less valence electrons (excluding H and He) move
freely within the material and provide carriers for electric current.
These materials are called conductors (metals)
What are semi conductors?
Atoms with 4 valence electrons bond together, however, not as tight
as the ones in insulators. With some thermal excitation, some of these
electrons can escape from the bond providing small amount of
electrical carriers. Lacking of sufficient carriers, these materials do
not conduct electricity as well as conductors. They are called
semiconductors
What are the two types of semiconductors?
intrinsic and extrinsic
What happens to intrinsic conductors at 0K?
At 0
0K, the valence electrons are shared between four other Si atoms forming
covalent bonds
What happens to intrinsic conductors at room temperature?
At room temperature, the valence electrons may gain thermal energy to break the
covalence bond and escape from its original position
What happens to intrinsic conductors as temperature increases?
As temperature increases, more electrons will be free increasing the conductivity
How can you create extrinsic conductors?
Another way of increasing the conductivity of semiconductors is doping, which
results in an extrinsic semiconductor
What is an n-type semiconductor?
Group V atoms in Si are called donor impurities. Semiconductor
containing donors is called n-type semiconductor.
What is a p-type semiconductor?
Group III atoms in Si are called acceptor impurities. Semiconductor
containing acceptors is called p-type semiconductor.
What occurs in a PN junction? (4)
Free electrons from the N-type region diffuse across the junction to the P-type
region. They recombine with some of the many holes in the P-type region
Similarly, holes diffuse across the junction in the opposite direction
Recombination of these charges create a narrow region which is called the depletion region.
The separation of these charges creates an electric field across the depletion
region called a built-in voltage
What is a diode?
Diode is a PN junction which allows current to pass in one direction – From the
P-type (called the anode) to the N-type (called the cathode) semiconductor
