Mosfet fundamentals
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The document discusses the fundamentals of MOSFETs (metal-oxide-semiconductor field-effect transistors). It describes the structure of an n-channel MOSFET, including the gate, body, source, and drain. It explains the different operating modes - depletion, enhancement - for n-channel and p-channel MOSFETs depending on the applied gate-source voltage. Finally, it notes that MOSFETs are generally considered three-terminal devices due to the body effect, which influences the threshold voltage.
Mosfet fundamentals
- 1. MOSFET Fundamentals Arpan Deyasi Dept of ECE, RCCIIT, Kolkata, India 5/31/2021 1 Arpan Deyasi, RCCIIT, India
- 2. 5/31/2021 Arpan Deyasi, RCCIIT, India 2 Al-SiO2-Si(p) under different biasing conditions Ec EV EFP Ei Al SiO2 Si VM>0 & small Depletion VM>0 & large Al SiO2 Si 1 2 point of inversion 3 Inversion ΨF ΨS
- 3. 5/31/2021 3 Arpan Deyasi, RCCIIT, India ΨF ΨS p n Conductor Insulator VM>0 & large
- 4. 5/31/2021 4 Arpan Deyasi, RCCIIT, India Semiconductor (p-substrate) Insulator Conductor n+ n+ n region (formed due to inversion)
- 5. 5/31/2021 5 Arpan Deyasi, RCCIIT, India Structural review of MOSFET MOSFET is a 4-terminal device Gate (conducting layer at top) Body (semiconducting substrate at bottom) Source (from where carriers start to flow) Drain (where carriers are collected) Body Channel Insulator Gate S D n-channel MOSFET / n-MOSFET
- 6. 5/31/2021 6 Arpan Deyasi, RCCIIT, India p-MOSFET n-MOSFET Body Channel Insulator Gate S D Body Channel Insulator Gate D S
- 7. 5/31/2021 7 Arpan Deyasi, RCCIIT, India Different Modes of Operation MOSFET type Operating mode VGS positive VGS = 0 volt VGS negative n-channel Depletion ON ON OFF Enhancement ON OFF OFF p-channel Depletion OFF ON ON Enhancement OFF OFF ON
- 8. 5/31/2021 8 Arpan Deyasi, RCCIIT, India Symbols of MOSFET under Different Modes p-MOSFET n-MOSFET
- 9. 5/31/2021 9 Arpan Deyasi, RCCIIT, India Why MOSFET is generally considered a three-terminal device? Ans: Body Effect
- 10. 5/31/2021 Arpan Deyasi, RCCIIT, India 10 Body Effect in n-channel MOSFET Body Channel Insulator Gate S (n+) D (n+) (p) (p)
- 11. 5/31/2021 Arpan Deyasi, RCCIIT, India 11 Body Effect in p-channel MOSFET Body Channel Insulator Gate D (p+) S (p+) (n) (n)