ANNIE KLOPP | Manga Part 4 156-195

Please skip over Chapter 4 and read Chapter 5 (pp. 156-195) in Manga Guide to Electricity

Please answer the following on the blog:
1. What is an example of a semiconductor device?

"A semiconductor is something that has properties in between those of a conductor, through which electricity easily passes, and an insulator, through which electricity has difficulty passing (Manga, 166).

Two examples of semiconductors (falls between conductor and insulator on the resistivity spectrum) are silicon and germanium.

2. Why is silicon used in the manufacture of semiconductors? 

"There are also cases in which a small amount of an impurity is mixed with the silicon or germanium... Normally, silicon is found in a substance called silicon dioxide, which is a refined product often used as the raw material for semiconductor devices" (Manga, 169).

Eventually a material with valence electrons is mixed with the silicon and creates free electrons.  "This causes the electrical conductivity of the semiconductor to increase" (Manga, 171).  

Basically, silicon is mixed in with semiconductors to make them more powerful. 

3. Discuss the difference using an example of the difference between and N-type and P-type semiconductor.

N-types are negative and P-types are positive.  

UPDATE (12:20AM 11/12/2015):  "If the crystalline array is 'doped' (mixed with an impurity) with arsenic which has five valence electrons, the behavior of the lattice will change. Four bonds will be still be made but there will be a leftover electron that can wander through the crystal. This is called an n-type semiconductor" (emsb.qc.ca) 

"Boron can also be used to dope a purse crystal of silicon.  But since boron only offers 3 of the four electrons that a silicon atom needs, each silicon center is left with a hole. Semiconductors made in this manner are called p-type" (emsb.qc.ca)

"N and P refers to the way current is carried in different types of semiconductor [sic]. In an N type, current is carried by electrons. In a P type, current is carried by the absence of electrons. "holes". Hole conduction is slower than electron conduction. Steve" (instructables.com, username: "steveastrouk")

"a bipolar transistor consists of a three-layer "sandwich" of doped (extrinsic) semiconductor materials, either P-N-P... or N-P-N.  Each layer forming the transistor has a specific name and each layer is provided with a wire contact for connection to a circuit" (allaboutcircuits.com)

The functional difference between a PNP transistor and an NPN transistor is the proper biasing (polarity) of the junctions when operating. For any given state of operation, the current directions and voltage polarities for each kind of transistor are example opposite each other (allaboutcircuits.com) 

"An N-type semiconductor... has a negative electrical property [and] becomes a carrier of electricity" (Manga, 166).

Examples of n-type semiconductors are Arsenic (As) or Phosphorus (P) (solarwiki.ucdavis.edu)

Examples of P-type semiconductors are Boron (B) or Aluminum (hyperphysics.phy-astr.gsu.edu)

The Aluminum semiconductor creates a deficiency of valence electrons, creating a hole, while the Arsenic contributes free electrons increasing the conductivity of the semiconductor.  

4. In your own words describe what a diode does and the role of N and P type semiconductors.

"If a P-type semiconductor and N-type semiconductor are combined to form a structure called a P-N junction, a semiconductor device called a diode is created" (164).

The flow of electricity is caused by the deficiency in the N-type, when placed against the P-type. 

5. What is rectification?

"The property that allows current to flow only in one direction" (173).

6. What causes color in an LED? Give and example of what causes a particular color.

"The wavelength of the light emitted depends on the raw material of the semiconductor [creating] various colors of light" (175).

Indium gallium nitride is used to make up the blue, white, true green and UV types.  Aluminum gallium indium phosphide is used to make the red, yellow, and orange types (led.linear1.org). 

7. What is the relationship between base current and collector current in a transistor?

"When the base current flows, the collector current will also flow"

"Transistors enable the collector current to become much greater than the base current"

"As a result, the collector current will change significantly in response to a slight change in the base current" (180).

8. What are the advantages of a transistor over a switch? 

"A transistor can also be used as a contactless switch" (181). 

"Unlike a regular switch, it has no physical contact, so it doesn't wear out and is less likely to fail.

Also, since it can be turned on and off rapidly, control can be fine tuned" (182).