Introducing
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
Semi-Conductors Mind Map
82
Semi-Conductors Mind Map
By: Latheeshan Suthaharan
Vacuum Tubes
Diodes/Triodes
Vacuum Tubes
- The oscilloscope was a development of the vacuum tube
- Beam is aimed at one end of the tube, shaped to form a circular screen
2) Triode
- Used to amplify currents.
- Is a vacuum tube with a third electrode (called the grid)
- A small negative voltage is applied to the grid, which holds electrons back
- Many different types of vacuum tubes
- Contained low pressure gas
- Used in the past, now replaced by transistors
- 1) Diode:
- Contains 2 electrodes, a cathode and anode
- Cathode is heated to give off electrons
- Positive Voltage = Anode Attracts Electrons
- Negative Voltage/Cold = Electrons don't flow
- One way device, called a rectifier
- Used when AC is needed to be turned into DC
Semiconductor Materials
Conductors, Insulators, Semiconductors
Semiconductor Materials
1) Conductors (metals)
- Current flows more when there is a greater voltage
2) Insulator (rubber, plastics)
- Few free electrons flowing
- Large voltages can be applied without currents flowing as much
3) Semiconductor (germanium, silicon, gallium)
- Few free electrons at low temperatures
- More free electrons as temperature increases
- As temps increase, atoms vibrate more, allowing electrons to move free
Energy Levels
- Atoms arrange electrons in energy levels
- Each shell holds a limited number of electrons
- Innermost shell holds 2 electrons
- Next shell holds 8 electrons
- Shell after can hold 8 or 18 electrons
- Elements that conduct electricity well easily lose their electrons in the outermost shell
- Silicon has 14 electrons, which means it has 2 full shells, and 4 remaining electrons
- Silicon is considered a semiconductor as the element can share electrons, and can form charge carriers
Energy Levels
Impurity Semiconductors
Impurity Semiconductors
- Adding small impurities of atoms increases charge carriers
- 2 types of semiconductors:
- n-type (negative)
- p-type (positive)
- n-type: mobile charge carriers consist of negatively charged electrons
- p-type: charge mostly carried by holes
(a hole is a gap that is found when an atom is short of a filled shell with an electron)
Transistors vs. Vacuum Tubes
Transistors
and
Vacuum Tubes
- The first transistor was a tiny device that performed the same job of a bulky triode
- It amplified voltage
- If a weak signal was applied, a larger voltage was made of the same wave pattern
- Transistors did not need to be heated, and used less energy than tubes
- It is more reliable
- The first design was improved, and a few years later products started using semiconductors
- Semiconductor diodes replaced vacuum tubes
Solid-State Devices
Negative Electrons & Positive Holes
Solid-State Devices
1) Solid State Diode
- Consists of a p-type semiconductor with contact of a n-type semiconductor
- Junction: A boundary between 2 types of material
- A piece of p-type material can be made inside of n-type material by adding impurity atoms of different kinds
Forward Bias
Forward Bias:
- p-type terminal connected to positive side of battery
- n-type terminal connected to negative side of battery
- Battery pushes electrons into n-type, and positive terminal attracts electrons out of p-type
Forward Bias
Reverse Bias
Reverse Bias
- Connections to the battery reversed are reverse bias
- In n-type material, electrons are pulled outwards from the junction
- Negatively charge electrons are removed, leaving behind a positive charge
- This positive charge pulls in electrons and stops them from being pulled any further away
- The holes in p-type material are pulled away from the junction and stop
- This means current cannot flow through
- This is useful for devices that requires current to flow in one way
Junction Transistor
Junction Transistor
- Consists of 3 types of semiconductors combined together
- p-type in between 2 pieces of n-type
- n-type in between 2 pieces of p-type
- Single piece of semiconductor, with different p-type and n-type regions
- These are npn and pnp transistors
- In these transistors, the middle part is called the base, the 2 other ends are called the emitter and the collector
- Works like 2 semiconductor diodes back to back
Field-Effect Transistor
- Also known as the FET
- Consists of a piece of n-type material (known as the channel)
- The p-type region, known as the gate, is on both sides of it
- Positive voltage is entered through the right end, and electrons move into the device at the left end (known as the source)
- Negative voltage applied = reverse-biased
- In FET, small changes in the gate voltage cause large changes in current that moves through the device, which allows it to amplify signals
Field-Effect Transistor
Making Chips
Microchips are chips of Semiconductors
Making Chips
- Making electronics smaller began during the creation of printed circuit boards
- PCB: made from a piece of copper foil connected to a plastic base. This copper is made into pathways that provide intersections between parts that are added by the user
Integrated circuits:
- Essential part is printing the circuit design onto a board
- An integrated circuit is made of different electronic parts formed into a single piece of semiconductor material
Making Microchips:
- Made from a rod of pure crystal semiconductor
- Made so that there is less than one impurity atom in every 1 billion
- There are wanted impurities, such as boron or indium, which is what is needed to make silicon into p-type material
Thank You