Presentation is loading. Please wait.

Presentation is loading. Please wait.

Day 10: September 26, 2012 MOS Transistor Basics

Published byHester Bailey Modified over 5 years ago

Similar presentations

Presentation on theme: "Day 10: September 26, 2012 MOS Transistor Basics"— Presentation transcript:

1 Day 10: September 26, 2012 MOS Transistor Basics
ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 10: September 26, 2012 MOS Transistor Basics Penn ESE370 Fall DeHon

2 Today MOS Transistor Topology Threshold Operating Regions Resistive
Saturation Velocity Saturation Subthreshold Penn ESE370 Fall DeHon

3 Last Time Penn ESE370 Fall DeHon

4 Refinement Depletion region  excess carriers depleted
Penn ESE370 Fall DeHon

5 Body Contact Fourth terminal Also effects fields
Usually common across transistors Penn ESE370 Fall DeHon

6 No Field VGS=0, VDS=0 Penn ESE370 Fall DeHon

7 Apply VGS>0 Accumulate negative charge Repel holes (fill holes)
Penn ESE370 Fall DeHon

8 Channel Evolution Increasing Vgs
Penn ESE370 Fall DeHon

9 Gate Capacitance Changes based on operating region.
Happy if you treat as parallel plate Capacitor for HW4. Penn ESE370 Fall DeHon

10 Inversion Surface builds electrons Inverts to n-type
Draws electrons from n+ source Penn ESE370 Fall DeHon

11 Threshold Voltage where strong inversion occurs  threshold voltage
Around 2ϕF Engineer by controlling doping (NA) Penn ESE370 Fall DeHon

12 Resistive Region VGS>VT, VDS small Penn ESE370 Fall DeHon

13 Resistive Region VGS>VT, VDS small VGS fixed  looks like resistor
Current linear in VDS Penn ESE370 Fall DeHon

14 Linear (Resistive) Region
Penn ESE370 Fall DeHon

15 Linear (Resistive) Region
Blue curve marks transition from Linear to Saturation Penn ESE370 Fall DeHon

16 Dimensions Channel Length (L) Channel Width (W) Oxide Thickness (Tox)
Penn ESE370 Fall DeHon

17 Preclass Ids for identical transistors in parallel?
Penn ESE370 Fall DeHon

18 Preclass Ids for identical transistors in series? (Vds small)
Penn ESE370 Fall DeHon

19 Transistor Strength (W/L)
D Transistor Strength (W/L) Penn ESE370 Fall DeHon

20 Transistor Strength (W/L)
D Transistor Strength (W/L) Shape dependence match Resistance intuition Wider = parallel resistors  decrease R Longer = series resistors  increase R Penn ESE370 Fall DeHon

21 Ldrawn vs. Leffective Doping not perfectly straight Spreads under gate
Effective L smaller than draw gate width Penn ESE370 Fall DeHon

22 Channel Voltage Voltage varies along channel
Think of channel as resistor Penn ESE370 Fall DeHon

23 Preclass 2 What is voltage in the middle of a resistive medium?
(halfway between terminals) Penn ESE370 Fall DeHon

24 Voltage in Channel Think of channel as resistive medium
Length = L Area = Width * Depth(inversion) What is voltage in the middle of the channel? L/2 from S and D ? Penn ESE370 Fall DeHon

25 Channel Voltage Voltage varies along channel
If think of channel as resistor Serves as a voltage divider between VS and VD Penn ESE370 Fall DeHon

26 Impact on Inversion What happens when What is Vmiddle-Vs? Vgs=2Vth ?
Vds=2Vth? What is Vmiddle-Vs? Penn ESE370 Fall DeHon

27 Channel Field When voltage gap VG-Vxdrops below VTH, drops out of inversion Occurs when: VGS-VDS< VTH What does this mean about conduction? Penn ESE370 Fall DeHon

28 Preclass 3 What is Vm? Penn ESE370 Fall DeHon

29 Channel Field When voltage gap VG-Vxdrops below VT, drops out of inversion Occurs when: VGS-VDS< VT What is voltage at Vmiddle if conduction stops? What does that mean about conduction? Penn ESE370 Fall DeHon

30 Contradiction? Vg-Vx < Vt  cutoff (no current)
No current  Vg-Vx=Vgs Vg-Vx=Vgs > Vt  current flows Penn ESE370 Fall DeHon

31 Way out? Vg-Vx < Vt  cutoff (no current) No current  Vg-Vx=Vgs
Vg-Vx=Vgs > Vt  current flows Act like Vds at Vgs-Vt Penn ESE370 Fall DeHon

32 Channel Field When voltage gap VG-Vxdrops below VT, drops out of inversion Occurs when: VGS-VDS< VT Channel is “pinched off” Penn ESE370 Fall DeHon

33 Channel Field When voltage gap VG-Vxdrops below VT, drops out of inversion Occurs when: VGS-VDS< VT Channel is “pinched off” Current will flow, but cannot increase any further Penn ESE370 Fall DeHon

34 Pinch Off When voltage drops below VT, drops out of inversion
Occurs when: VGS-VDS< VT Conclusion: current cannot increase with VDS once VDS> VGS-VT Penn ESE370 Fall DeHon

35 Saturation In saturation, VDS-effecitve=Vx= VGS-VT Becomes:
Penn ESE370 Fall DeHon

36 Saturation VDS> VGS-VT Penn ESE370 Fall DeHon

37 Saturation Region Blue curve marks transition from Linear
to Saturation Penn ESE370 Fall DeHon

38 Preclass 3 What is electrical field in channel? Velocity: v=F*μ
Leff=25nm, VDS=1V Field = VDS/L Velocity: v=F*μ Electron mobility: μn = 500 cm2/V What is electron velocity? Penn ESE370 Fall DeHon

39 Short Channel Model assumes carrier velocity increases with field
Increases with voltage There is a limit to how fast carriers can move Limited by scattering to 105m/s How relate to preclass 3 velocity? Encounter when channel short Modern processes, L is short enough Penn ESE370 Fall DeHon

40 Velocity Saturation Once velocity saturates:
Penn ESE370 Fall DeHon

41 Velocity Saturation Penn ESE370 Fall DeHon

42 Below Threshold Transition from insulating to conducting is non-linear, but not abrupt Current does flow But exponentially dependent on VGS Penn ESE370 Fall DeHon

43 Subthreshold Penn ESE370 Fall DeHon

44 Subthreshold S D W/L dependence follow from resistor behavior (parallel, series) Not shown explicitly in text λ is a channel width modulation effect Penn ESE370 Fall DeHon

45 Subthreshold Slope Exponent in VGS determines how steep the turnoff is
Every S Volts Divide IDS by 10 Penn ESE370 Fall DeHon

46 Subthreshold Slope Exponent in VGS determines how steep the turnoff is
Every S Volts (S not related to source) Divide IDS by 10 n – depends on electrostatics n=1  S=60mV at Room Temp. (ideal) n=1.5  S=90mV Single gate structure showing S=90-110mV Penn ESE370 Fall DeHon

47 IDS vs. VGS Penn ESE370 Fall DeHon

48 Admin Text 3.3.2 – highly recommend read HW3 due Thursday HW4 out
Second half on Friday HW3 due Thursday HW4 out Penn ESE370 Fall DeHon

49 Big Idea 3 Regions of operation for MOSFET Subthreshold Resistive
Saturation Pinch Off Velocity Saturation Short channel Penn ESE370 Fall DeHon

Download ppt "Day 10: September 26, 2012 MOS Transistor Basics"

Similar presentations

EE466: VLSI Design Lecture 02 Non Ideal Effects in MOSFETs.

EE466: VLSI Design Lecture 02 Non Ideal Effects in MOSFETs.
Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory David Harris Harvey Mudd College Spring 2004.

Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory David Harris Harvey Mudd College Spring 2004.
VLSI Design CMOS Transistor Theory. EE 447 VLSI Design 3: CMOS Transistor Theory2 Outline Introduction MOS Capacitor nMOS I-V Characteristics pMOS I-V.

VLSI Design CMOS Transistor Theory. EE 447 VLSI Design 3: CMOS Transistor Theory2 Outline Introduction MOS Capacitor nMOS I-V Characteristics pMOS I-V.
EE415 VLSI Design The Devices: MOS Transistor [Adapted from Rabaey’s Digital Integrated Circuits, ©2002, J. Rabaey et al.]

EE415 VLSI Design The Devices: MOS Transistor [Adapted from Rabaey’s Digital Integrated Circuits, ©2002, J. Rabaey et al.]
Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory

Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory
CSCE 612: VLSI System Design Instructor: Jason D. Bakos.

CSCE 612: VLSI System Design Instructor: Jason D. Bakos.
Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory David Harris Harvey Mudd College Spring 2004 from CMOS VLSI Design A Circuits and Systems.

Introduction to CMOS VLSI Design Lecture 3: CMOS Transistor Theory David Harris Harvey Mudd College Spring 2004 from CMOS VLSI Design A Circuits and Systems.
Week 8b OUTLINE Using pn-diodes to isolate transistors in an IC

Week 8b OUTLINE Using pn-diodes to isolate transistors in an IC
Lecture 2: CMOS Transistor Theory

Lecture 2: CMOS Transistor Theory
VLSI design Lecture 1: MOS Transistor Theory. CMOS VLSI Design3: CMOS Transistor TheorySlide 2 Outline  Introduction  MOS Capacitor  nMOS I-V Characteristics.

VLSI design Lecture 1: MOS Transistor Theory. CMOS VLSI Design3: CMOS Transistor TheorySlide 2 Outline  Introduction  MOS Capacitor  nMOS I-V Characteristics.
MOS Capacitors ECE 2204. Some Classes of Field Effect Transistors Metal-Oxide-Semiconductor Field Effect Transistor ▫ MOSFET, which will be the type that.

MOS Capacitors ECE Some Classes of Field Effect Transistors Metal-Oxide-Semiconductor Field Effect Transistor ▫ MOSFET, which will be the type that.
Metal-Oxide-Semiconductor Field Effect Transistors

Metal-Oxide-Semiconductor Field Effect Transistors
Lecture 3: CMOS Transistor Theory

Lecture 3: CMOS Transistor Theory
Qualitative Discussion of MOS Transistors. Big Picture ES220 (Electric Circuits) – R, L, C, transformer, op-amp ES230 (Electronics I) – Diodes – BJT –

Qualitative Discussion of MOS Transistors. Big Picture ES220 (Electric Circuits) – R, L, C, transformer, op-amp ES230 (Electronics I) – Diodes – BJT –
ECE 342 Electronic Circuits 2. MOS Transistors

ECE 342 Electronic Circuits 2. MOS Transistors
Penn ESE370 Fall2014 -- DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 12: September 24, 2014 MOS Transistor.

Penn ESE370 Fall DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 12: September 24, 2014 MOS Transistor.
Penn ESE370 Fall2011 -- DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 10: September 28, 2011 MOS Transistor.

Penn ESE370 Fall DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 10: September 28, 2011 MOS Transistor.
1 Slides adapted from: N. Weste, D. Harris, CMOS VLSI Design, © Addison-Wesley, 3/e, 2004 MOS Transistor Theory.

1 Slides adapted from: N. Weste, D. Harris, CMOS VLSI Design, © Addison-Wesley, 3/e, 2004 MOS Transistor Theory.
Qualitative Discussion of MOS Transistors. Big Picture ES230 – Diodes – BJT – Op-Amps ES330 – Applications of Op-Amps – CMOS Analog applications Digital.

Qualitative Discussion of MOS Transistors. Big Picture ES230 – Diodes – BJT – Op-Amps ES330 – Applications of Op-Amps – CMOS Analog applications Digital.
CSCE 613: Fundamentals of VLSI Chip Design Instructor: Jason D. Bakos.

CSCE 613: Fundamentals of VLSI Chip Design Instructor: Jason D. Bakos.

Similar presentations

Ads by Google