Siddarth Ram mohan arun What is A Mosfet M etal O xide S emiconductor F ield E ffect T ransistor Threeterminal device Source Drain and Gate Transistors are used for switching and amplification in circuits ID: 1031134
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1. MOSFETPRESENTED BY Vivek Krishna KannanSiddarth Ram mohan arun
2. What is A Mosfet?Metal Oxide Semiconductor Field Effect TransistorThree-terminal device: Source, Drain and GateTransistors are used for switching and amplification in circuits
3. Things to knowA semiconductor (eg: Si) has an electrical conductivity value between a conductor and an insulator.Current conduction occurs through free movement of electrons or holes.Doping introduces impurities into a pure semiconductor for the purpose of modulating its electrical properties.
4. How doping works
5. Device structure of n-channel Mosfet
6. The gate terminal is a conducting surface (Metal)The gate terminal is separated by a layer of insulator (oxide) from the channelThe (semiconductor) substrate is doped with p-type impuritySource and Drain are doped with n-type impurityThe gate, source and drain have conducting metal contacts Device structure of enhancement mode n-channel Mosfet
7. Perspective viewCross sectional view
8. Device structure of p-channel Mosfet
9. Circuit Symbols commonly used
10. Further classifications In addition to NMOS & PMOS explained earlier, they can in turn be further classified intoEnhancement modeDepletion mode
11. What is Enhancement mode ?Enhancement mode MOSFETS comes devoid of a “channel”Depletion mode comes with a channel by defaultA channel can roughly be described as a conduction path that enables the MOSFET to work
12. How does enhancement mosfet work without a channel ?This is where the gate voltage plays a significant partGate voltage serves to create the channel in enhancement mode, while in depletion mode it cane be used to “deplete” the channel; As in destroy.Enhancement mode and depletion mode can be summarized as normally open and normally closed switches respectively.
13. Conduction in an enhancement mode n-MosfetCreation of the channel by applying gate voltageThreshold voltage : Gate voltage must be higher than Vt, only then is the conduction path createdChannel is just the ‘path’; Additional potential difference is needed to instigate and sustain charge flow. This is provided by applying a potential difference voltage between drain and source terminals
14. I-v characteristics of MOsfetThe plot is between the drain current and the drain-source voltage, for different values of gate voltageMOSFET operating regions:Cutoff modeTriode/Linear modeSaturation mode
15. ApplicationsMicroprocessors for switching purposesRadio frequency amplifiers