Definition • An electronic device made of a semiconductor that can act as an insulator and a conductor. • The ability to change from these two states enables the device switch or amplify. • It has of three components: • Source • Gate • Drain
Transistors • Transistors replaced vacuum tubes. • Transistors are central to the Integrated Circuit, and • therefore, all electronic devices of the information age, such as: • pc’s, cellular phones, ipods, pda’s, intelligent cars and buildings…….. are made possible.
How a Transistor Works • The transistor can function as: • An insulator • A conductor • The transistor's ability to fluctuate between these two states that enables to switch or amplify. ◄
How a Transistor Works • The transistor has many applications, but only two basic functions: • switching and modulation (amplification). • In the simplest sense, the transistor works like a dimmer.
How a Transistor Works • With a push the knob of the dimmer, the light comes on and off. • You have a switch. • Rotate the knob back and forth, and the light grows brighter, dimmer, brighter, dimmer. • Then you have a modulator.
How a Transistor Works cont. • Both the dimmer and the transistor can control current flow. • Both can act as a switch and as a modulator/amplifier. • The important difference is that the “hand” operating the transistor is millions of times faster. ◄
Transistors are made of semi-conductors such as silicon and gallium arsenide. These materials carry electricity not well enough to be called conductors; not badly enough to be called insulators. How a Transistor Works cont. ◄
How a Transistor Works cont. • Hence their name semiconductor. • The importance of a transistor is in its ability to control its own semi conductance, • namely acting like a conductor when needed, or as an insulator (nonconductor) when that is needed.
How a Transistor Works cont. • You can compare a transistor to an ordinary faucet. • The water enters the faucet in the pipeline from the water distributor, which would correspond to the source in the Transistor. • The water then leaves the faucet into the sink, this would be the drain in the Transistor. ◄
How a Transistor Works cont. • The water tap controls the amount, flow, of water. • In the Transistor the gate operates as this controller. • With a small force you can control the water flow with the water tap, just as you can control the current flowing from the source to the drain, with a small change of the charge of the gate.
Transistors are Made of Silicon • Silicon is a grey colored element with crystalline structure. • It is the second most abundant element in the earth's crust, after oxygen. • Silicon is always found in combined form in nature, often with oxygen as quartz, and is found in rocks and silica sand. ◄
Transistors are Made of Silicon • To be able to use silicon as a semiconductor, it needs to be in a very pure form. • If there is more than one impure particle in a million, the silicon can not be used. • Silicon is the most frequently used semiconducting material today.
Doping • The addition of a small amount of a different substance to a pure semiconductor crystal. • The impurities give an excess of conducting electrons or an excess of conducting holes which is crucial for making a working transistor. ◄
Conduction Band Is a part in which electrons can move freely and can accelerate under an electric field, constituting an electric current. Energy Gap: Is the energy difference between the valence gap and the conduction band Valence Band: Is a part of the molecule, called band, where you can find the electrons ◄
Conduction Band Metals Valence Band Conduction Band Semiconductors Energy gap Valence Band Conduction Band Bigger Energy gap Insulators Valence Band
Transistor types • MOS - Metal Oxide Semiconductor • FET - Field Effect Transistor • BJT - Bipolar Junction Transistor ◄
Moore’s Law • It’s an observation made by Gordon E. Moore, in which he predicted that the number of transistors, inside an Integrated Circuit, could be doubled every 24 months. • At the density that also minimized the cost of a transistor. ◄
Pictorial History of Transistors ◄ http://www.bellsystemmemorial.com/belllabs_transistor.html