1 / 12

MOSFET Structure

Gate Oxide. Source. Gate. Drain. Field Oxide. n +. L. p-Si. Bulk (Substrate). MOSFET Structure. Importance for LSI/VLSI Low fabrication cost Small size Low power consumption Applications Microprocessors Memories Power Devices Basic Properties Unipolar device

nam
Download Presentation

MOSFET Structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Gate Oxide Source Gate Drain Field Oxide n+ L p-Si Bulk (Substrate) MOSFET Structure

  2. Importance for LSI/VLSI • Low fabrication cost • Small size • Low power consumption • Applications • Microprocessors • Memories • Power Devices • Basic Properties • Unipolar device • Very high input impedance • Capable of power gain • 3/4 terminal device, G, S, D, B • Two possible device types: enhancement mode; depletion mode • Two possible channel types: n-channel; p-channel

  3. D D B B G G S S Symbols p Channel MOSFET n Channel MOSFET

  4. D IDS C B A VDS Current-Voltage Characteristic

  5. S D VG +VDS p-Si n-Channel B Channel Formation

  6. Analysis: Low VDS(A)

  7. Source Channel Drain VT VG VG-channel VDS VDS/2 Intermediate VDS(B)

  8. S D VG +VDS p-Si n-Channel B Increased VDS

  9. Analysis: Intermediate VDS • First Order Approximation • Gate to Channel Voltage = VGS-VDS/2 Extra term!

  10. Source Channel Drain VG-channel VDS VG VT Pinch-off Large VDS: Saturation (C)

  11. Analysis: Saturation (C) Pinch-off Substitute for VDS(sat) in equation for IDS to get IDS(sat)

  12. Avalanche and Punch-Through(D) • For very large VDS, IDS increases rapidly due to drain junction avalanche. • Can give rise to parasitic bipolar action. • In short channel transistors, the drain depletion region may reach the source depletion region giving rise to ‘Punch Through’.

More Related