eecs 312 discussion 3

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EECS 312 Discussion 3 09/20 Shengshuo Lu ([email protected])

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EECS 312 Discussion 3. 09/20 Shengshuo Lu ([email protected]). Overview. Reminder HW 1: Due Sep 24 Diode Transistors. Diode. G. S. D. Diode. Diode. Built-in Potential Depletion Region Width. Diode Current. Diffusion capacitance. NMOS. G. S. D. Threshold Voltage. - PowerPoint PPT Presentation

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Page 1: EECS 312 Discussion 3

EECS 312 Discussion 3

09/20Shengshuo Lu

([email protected])

Page 2: EECS 312 Discussion 3

Overview

• Reminder– HW 1: Due Sep 24

• Diode

• Transistors

Page 3: EECS 312 Discussion 3

Diode

G

S D

Page 4: EECS 312 Discussion 3

Diode

Page 5: EECS 312 Discussion 3

Diode

Page 6: EECS 312 Discussion 3

Built-in PotentialDepletion Region Width

Page 7: EECS 312 Discussion 3

Diode Current

Page 8: EECS 312 Discussion 3

Diffusion capacitance

Page 9: EECS 312 Discussion 3

NMOS

G

S D

Page 10: EECS 312 Discussion 3

Threshold Voltage

• 0 < VGS < VT

– Repel mobile holesand accumulation of electron beneaththe gate oxide

• VGS > VT

– Surface is as strongly n-type asthe substrate is p-type

VGS VT

RonS D

Page 11: EECS 312 Discussion 3

Operation Regions – Linear (lab 2)

1. VGS > VT

2. VGS – VT > VDS

3. Linear contribution of VGT to ID

4.

In case of a P-type MOSFET, the inequalities used above should be directed opposite

Page 12: EECS 312 Discussion 3

Operation Regions – Saturation (lab 2)

1. VGS > VT

2. VGS – VT ≤ VDS

3. Quadratic contribution of VGTto ID

4. channel-length modulation parameter

In case of a P-type MOSFET, the inequalities used above should be directed opposite

Page 13: EECS 312 Discussion 3

Operation Regions – Velocity Saturated

LinearDependence

-4

VDS (V)0 0.5 1 1.5 2 2.5

0

0.5

1

1.5

2

2.5x 10

I D (A

)

VGS= 2.5 V

VGS= 2.0 V

VGS= 1.5 V

VGS= 1.0 V

Early Saturation

Strong electric field causes carrier mobility degradation : Compared to feature scaling, voltage scaling is lagging behind

Short Channel Effects

Page 14: EECS 312 Discussion 3

A unified model

1. If VDS is minimum: Linear region

2. If VGT is minimum:Saturation Region

3. If VDSAT is minimum : Velocity saturated region