How Semi Conductors Work
Semiconductors have an enormous impact on our daily lives and on society in general. They are key electrical components in virtually every electronic device we own, and we have a lot of them. The semiconductor is central to transistors as well as microprocessor chips. Many of our most commonly used items are now computerized, including our vehicles, and anything that is computerized makes use of radio waves and are dependent on semiconductors.
What is a semiconductor?
Most of the semiconductors and transistors are made of silicon which is a very common element. It is actually the primary element found in both quartz and sand. Silicon is located on the periodic table right next to aluminum, above germanium and below carbon. Germanium, carbon and silicon are structured uniquely in that they all have four electrons in their outer orbital. This is good because it allows them to form crystals. These four electrons work together to form perfect bonds with four neighboring atoms to form a type of lattice. The crystalline form of carbon is a diamond and the crystalline form in silicon is a silvery metallic substance. Metals are typically very good electrical conductors since they contain “free electrons” that can very easily move between atoms which allows for electricity to flow freely as well. Silicon’s outer electrons create perfect bonds which means that they cannot move about. Pure silicon crystal is more of an insulator since there is very little electricity allowed to flow through it. But the amount of electricity that flows through conductors can be changed through the process of doping.
What is doping?
Silicon’s primary behaviors are transformed through a process called doping. This is where small amounts of impurities are mixed into the silicon crystal. There are two different types of impurities: N-type and P-type. A very small amount of either impurity will turn silicon into a conductor instead of an insulator. When P and N types of silicon are placed together, there are some very interesting behaviors that occur. This is where a diode comes from. A diode is the simplest semiconductor. It allows the current to flow in one direction but not in the other. Think about how a turnstile works by allowing crowds to go in one direction only. The diode acts like a one-way turnstile for the electrons. Both the N-type and P-type of silicon are conductors by themselves.
Transistors and Diodes
Diodes are used in a variety of ways. Devices that use batteries may contain diodes which will protect the device from damage if the batteries are put in backwards. The diode will simply work to bock the current from flowing the other direction as when the battery is reversed. A diode in a semiconductor isn’t perfect, but it can block most reverse currents. A diode may allow approximately 10 micro amps through – that’s not a lot. If enough reverse voltage is applied, the junction can break down and allow current through. But typically, the breakdown voltage is a lot more than the circuit would ever touch so it really won’t matter. The diode requires a small amount of voltage in order to get going. In silicon, it takes about 0.7 volts. This can start the hole-electron process. Transistors have a lot in common with diodes but instead of two layers like a diode, a transistor has three. A transistor can be either a PNP or an NPN sandwich. It can act as either an amplifier or a switch. Transistors look sort of like having two diodes positioned back to back. Since a single diode blocks current, and a transistor is like having them back to back it will block the current from both directions. But if a very small current is applied to the middle layer of the transistor’s “sandwich” it will allow a much larger current to flow through it as a whole. This allows a transistor to have a switching ability. Small currents can turn larger currents off and on. A silicon chip is made from a piece of silicon and it can hold literally thousands of transistors. Using transistors as switches can create a Boolean gate which is what creates a microprocessor chip. Microprocessors are made from using doped silicon to create a transistor and then a chip.
What is a semiconductor?
Most of the semiconductors and transistors are made of silicon which is a very common element. It is actually the primary element found in both quartz and sand. Silicon is located on the periodic table right next to aluminum, above germanium and below carbon. Germanium, carbon and silicon are structured uniquely in that they all have four electrons in their outer orbital. This is good because it allows them to form crystals. These four electrons work together to form perfect bonds with four neighboring atoms to form a type of lattice. The crystalline form of carbon is a diamond and the crystalline form in silicon is a silvery metallic substance. Metals are typically very good electrical conductors since they contain “free electrons” that can very easily move between atoms which allows for electricity to flow freely as well. Silicon’s outer electrons create perfect bonds which means that they cannot move about. Pure silicon crystal is more of an insulator since there is very little electricity allowed to flow through it. But the amount of electricity that flows through conductors can be changed through the process of doping.
What is doping?
Silicon’s primary behaviors are transformed through a process called doping. This is where small amounts of impurities are mixed into the silicon crystal. There are two different types of impurities: N-type and P-type. A very small amount of either impurity will turn silicon into a conductor instead of an insulator. When P and N types of silicon are placed together, there are some very interesting behaviors that occur. This is where a diode comes from. A diode is the simplest semiconductor. It allows the current to flow in one direction but not in the other. Think about how a turnstile works by allowing crowds to go in one direction only. The diode acts like a one-way turnstile for the electrons. Both the N-type and P-type of silicon are conductors by themselves.
Transistors and Diodes
Diodes are used in a variety of ways. Devices that use batteries may contain diodes which will protect the device from damage if the batteries are put in backwards. The diode will simply work to bock the current from flowing the other direction as when the battery is reversed. A diode in a semiconductor isn’t perfect, but it can block most reverse currents. A diode may allow approximately 10 micro amps through – that’s not a lot. If enough reverse voltage is applied, the junction can break down and allow current through. But typically, the breakdown voltage is a lot more than the circuit would ever touch so it really won’t matter. The diode requires a small amount of voltage in order to get going. In silicon, it takes about 0.7 volts. This can start the hole-electron process. Transistors have a lot in common with diodes but instead of two layers like a diode, a transistor has three. A transistor can be either a PNP or an NPN sandwich. It can act as either an amplifier or a switch. Transistors look sort of like having two diodes positioned back to back. Since a single diode blocks current, and a transistor is like having them back to back it will block the current from both directions. But if a very small current is applied to the middle layer of the transistor’s “sandwich” it will allow a much larger current to flow through it as a whole. This allows a transistor to have a switching ability. Small currents can turn larger currents off and on. A silicon chip is made from a piece of silicon and it can hold literally thousands of transistors. Using transistors as switches can create a Boolean gate which is what creates a microprocessor chip. Microprocessors are made from using doped silicon to create a transistor and then a chip.