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ST Semi
| Question | Answer |
|---|---|
| What is a semi conductor? | A material that can conduct electricity under certain conditions., such as changes in light or heat. It conducts better than an insulator like glass but not as well as a conductor like copper. Electrons only move in one direction. |
| Valance Band | It is the outermost orbit on an atom. Electrons are fixed in place. It is inside the conductive band. |
| Conduction Band | This band is outside the valance band. If electrons have enough energy to cross the band gao they will reach the conductive band in an atom, then the electrons are free to move to other atoms and make conductors. |
| What material is used to make semi conductors | Silicon |
| Silicon Properties | Melts at 1414 degrees. Hard Grey material. As it heats up it becomes more conductive |
| Applications of semi conductors | diodes, transistors, and integrated circuits, LDRs |
| Electrons in semi conductors occupy specific energy levels grouped into bands. Name 2 of the bands. | Valance Bands. Conduction Bands |
| Valance Band definition | electrons are tightly held, and electricity cannot flow. |
| Conduction Band | electrons are free to move and carry electricity |
| Insulator | A material that cannot conduct electricity |
| Band Gap | The energy difference between the valence and conduction bands |
| Doping | Improving the conductivity of semi conductors by adding impurities such as Boron or Phosphorous |
| Hole | When an electron moves up to the conduction band, from the valance band it leaves behind a hole. |
| Diode | allows current to flow in only one direction, like a one-way valve for electricity |
| Transistor | It acts as an electronic switch which stops or starts the flow of current, or an amplifier that controls the flow of large currents relative to the small change in the control signal from a sensor |
| Deposition | Layers of material are added to a wafer such as conductors ad insulators to build up the layers on a chip. |
| Photolithography | A process that transfers shapes from a template to a surface using UV light to build the patterns to allow semiconductor components to work eg in an Integrated Circuit |
| Etching | A chemical process which is used to remove material to produce the circuit pattern in electronic semi conductor components |
| Silicon Wafer | It is the material used to produce semi conductors. It is free from impurities. It is the starting layer of the semi conductor and is circular in shape |
| Logic Gates | Logic gates are the basic building blocks of any digital (1 / 0 ) system. It is an electronic circuit having one or more or input and only one output. It is based on Boolean Logic |
| Boolean Logic | This means a result that can only have one of two possible values: true or false (1 or 0 ) True = 1 False = 0 |
| Michael Faraday | Studied the conductivity of materials |
| John Bardeen, Walter Brattain, and William Shockley | Invented the transistor |
| LDR | Light dependent resistor. Resistance varies with light |
| Thermistor | Resistance varies with heat |
| N Type Semi Conductors | Semiconductor doped with phosphorus which has extra free electrons which can move. This makes the material negatively charged |
| P Type semi conductor | Doped with Boron. This creates 'Holes' or missing electrons. Electrons from nearby atoms jump into these holes creating positive charge carriers. |
| P N Junction | Where the N Type and P Type semi conductors are combined |
| Diode Forward Bias (Conducting) | When the positive side of the battery is connected to the P-type side, the depletion region narrows. Electrons and holes can cross the junction, and the diode allows current to flow. |
| Diode Reverse Bias (Blocking) | When the polarity is reversed, the depletion region widens. Electrons and holes are pulled away from the junction, and the diode blocks current. |
| Depletion region | The area where the N type and P type junction meet. It has both a positive and negative region. When in reverse biased mode, this region expands preventing current flow. |
| MOSFET ON | The conducting (ON ) state on a transistor |
| MOSFET OFF | The non conducting (OFF) state on a transistor |
| What is the difference between forward bias and reverse bias in a diode? | Forward bias makes a diode a conductor, while reverse bias makes it an insulator |
| Explain the meaning of 'digital Input'. | Digital means something is either On or Off. It is identified with 1 (One) and 0 (Zero) e.g. a normal light switch. |
| Explain the meaning of an analogue input. | It has a variety of On or Off states depending on current flow and resistance e.g. a dimmer switch. |
Created by:
Engineeringmcs