mosfet
TRANSCRIPT
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MOSFETThe metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of transistor used for amplifying or switching electronic signal.Although the MOSFET is a four-terminal device with source (S), gate (G), drain (D), and body (B) terminals, the body (or substrate) of the MOSFET is often connected to the source terminal, making it a three-terminal device like other field-effect transistor. Because these two terminals are normally connected to each other (short-circuited) internally, only three terminals appear in electrical diagrams. The MOSFET is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common.
CompositionUsually the semiconductor of choice is silicon, but some chip manufacturers, most notably IBM and Intel, recently started using a chemical compound of silicon and germanium in MOSFET channels. Unfortunately, many semiconductors with better electrical properties than silicon, such as gallium arsenide, do not form good semiconductor-to-insulator interfaces, and thus are not suitable for MOSFETs. Research continues on creating insulators with acceptable electrical characteristics on other semiconductor material.
What is the body effect in MOSFET?
NMOS consist of p type substrate and n type channel. If p substrate is at 0 V then the body effect is not present if it is at negative voltage then the holes in the p substrate gets attracted towards the negative voltage and leaves negative ions to satisfy space charge neutrality because of this extra negative ions the thickness of the depletion layer will be increased thus the threshold voltage is increased.
BODY EFFECTYou might have forgotten, but a transistor is a 4-terminal device. Gate, drain and source are the 3 terminals that are used to control the transistor, but the bulk or body, if not properly biased, may put the transistor inoperable
The p-n junctions defined by source-bulk and drain-bulk, which are basically two diodes, must be reverse-biased to stop them from leaking current from the source/drain to the substrate. That means that the source potential must always be equal or greater than the bulk potential. Since drain voltage is always greater or equal than source voltage, we don't even consider the drain-bulk junction.
The Difference Between NMOS & PMOS • NMOS is built with n-type source and
drain and a p-type substrate. • NMOS, carriers are electrons• When a high voltage is applied to the
gate, NMOS will conduct• When a low voltage is applied in the gate,
NMOS will not conduct • NMOS are considered to be faster than
PMOS, since the carriers in NMOS, which are electrons, travel twice as fast as holes.
• NMOS ICs would be smaller than PMOS Ics.
• NMOS represents N type MOS transistor.
• PMOS is built with p-type source and drain and a n-type substrate. • PMOS, carriers are holes.• When a high voltage is applied to the
gate, PMOS will not conduct• When a low voltage is applied in the
gate, PMOS will conduct • Which are the carriers in PMOS.• PMOS devices are more immune to
noise than NMOS devices. • PMOS represents P type MOS
transistor
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