ElectronicsI_L7 - Lecture 7 Transistors So far all we have...

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Lecture 7
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Transistors • So far all we have covered in the class are two terminal devices, except for the amplifier. • But in the case of the amplifier, we never looked at the circuit level operation of the device, just simple models of them. • If we want to actually amplify something, we need a way to have a separated input and output. – If the magnitude of the output is to be larger than the input, they must have different Kirchoff loops to follow. You can’t have two voltages/currents coming out of the same lead. – Two terminal devices are unable to put out a value larger than is out in (they are passive devices, with no power supply)
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Just a fancy switch • We need a three terminal device – A voltage, or current is applied across two terminals – The current out of the third terminal is dictated by that applied signal – The output can (and most times will) be greater than the input signal. • This class of devices is known as the transistor • We will study two kinds: – MOSFETs – BJTs • In this chapter we will look at the MOSFET
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The MOSFET MOSFET stands for Metal Oxide Field Effect Transistor This is simply a description of the physical layout of the device – There is a metal gate that is separated from the main body of the semiconductor by an insulator – The semiconductor has two terminals, located on either side of the gate. They are called the Source (S) and Drain (D) – Underneath the gate and between the source and drain is the channel The field effect part of the name refers to the fact that an electric field is used to control the conductivity of the channel. Note: MOSFET actually refers
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ElectronicsI_L7 - Lecture 7 Transistors So far all we have...

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