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The NFET explained… in only a few confusing slides.

The NFET explained… in only a few confusing slides. Voltage-controlled Current Source. D rain. V ds. G ate. I DS. d. V gs. g. Vds > Vgs-Vt. S ource. s. l << 1. 2. W. I DS = k ( ) ( V gs - V t ). (1 + l V ds ). L. Early Effect.

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The NFET explained… in only a few confusing slides.

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  1. The NFET explained… in only a few confusing slides.

  2. Voltage-controlled Current Source Drain Vds Gate IDS d Vgs g Vds > Vgs-Vt Source s l << 1 2 W IDS = k ( ) ( Vgs - Vt ) (1 + l Vds) L Early Effect Saturation Region:

  3. Ids Drain Vds Gate IDS Vgs Source Vt Vgs Fig 4-13 Vds > Vgs - Vt

  4. Ohmic (Triode) Region: 2 W IDS = k ( ) [ 2 (Vgs - Vt) Vds - Vds ] L Drain Vds < Vgs - Vt Gate IDS Source (Vds is small)

  5. Ids Vds Fig 4-12 Drain Gate IDS Source dotted line is what the previous graph plotted.

  6. depletion regions NFET - Operation gate = 0.0 v source = 0.0 v drain = 0.0 v n+ n+ p-type

  7. NFET - Operation (subthreshold) gate = 0.0 v source = 0.0 v drain = 0.0 v n+ n+ p-type

  8. depletion region NFET - Operation (subthreshold) gate = 0.4 v source = 0.0 v drain = 0.0 v n+ n+ p-type

  9. NFET - Operation (subthreshold) gate = 0.6 v source = 0.0 v drain = 0.0 v n+ n+ p-type

  10. ThresholdVoltage, Vgs = 0.75 v NFET - Operation A channel is formed…. gate = 0.75 v source = 0.0 v drain = 0.0 v n+ n+ inversion p-type

  11. Ids = 0.0 A NFET - Operation (above threshold) gate = 1.0 v source = 0.0 v drain = 0.0 v n+ n+ p-type

  12. NFET - Operation (above threshold) Ids = 10 uA gate = 1.0 v source = 0.0 v drain = .05 v n+ n+ p-type

  13. 0.05v 0.1v NFET - Operation (above threshold) Ids = 20 uA gate = 1.0 v source = 0.0 v drain = 0.1 v n+ n+ p-type

  14. NFET - Operation (above threshold) Ids = 40 uA gate = 1.0 v source = 0.0 v drain = 0.2 v n+ n+ 0.2v .05v 0.1v p-type

  15. Pinch-off NFET - Operation (above threshold) Vds > Vgs - Vt Ids = 59 uA gate = 1.0 v source = 0.0 v drain = 0.25 v n+ n+ 0.25v .05v 0.1v p-type

  16. NFET - Operation (above threshold) Vds > Vgs - Vt Ids = 60 uA gate = 1.0 v source = 0.0 v drain = 0.3 v n+ n+ 0.25v .05v 0.1v p-type

  17. NFET - Operation (above threshold) Vds > Vgs - Vt Ids = 61 uA gate = 1.0 v source = 0.0 v drain = 0.4 v n+ n+ = Vgs-Vt 0.25v .05v 0.1v p-type

  18. Fig 4-12 Ids NOTICE - the saturation region is now up where the current is constant for different VDS. the arrows indicate what we showed in the previous figures as Vds was increased for a fixed Vgs Vds

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