Reference Generators Part II Chapter 4 from Gray and Meyers book - - PowerPoint PPT Presentation

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Reference Generators – Part II

Chapter 4 from Gray and Meyer’s book Chapter 11 from Razavi’s book

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Slides Figures

• Unless it’s mentioned figures and contents of

slides are taken from: ‘Design of Analog CMOS Integrated Circuits’ by Behzad Razavi

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Temperature Variation Tolerant Vref - Negative Temperature Coefficient ( ) ( ) ( )

K mV T V V q E m V V T q E V m V T V V kT E T V m I I T V T V m where T e T n n kT I e I I

BE g BE g T BE BE T g T S C T BE m kT E i i s V V s c

g T BE



/ 2 273 2 . 1 0625 . 7 . 2 . 1 , 5 . 1 , 7 . : re temperatu room Example 4 4 ln 1 2 , , ,

2 3 2

− = − − = ∂ ∂ ⇒ = − = = − + − = ∂ ∂ ⇒ − + −         = ∂ ∂ ⇒ − < < − ∝ ∝ × × ∝ =

−

µ µ µ

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Temperature Variation Tolerant Biasing- Positive Temperature Coefficient

( ) ( ) ( ) ( )

n q KT n V T V V n V V V nI I I I I I V V BJT Q I I V V BJT Q

T BE BE T BE BE s s c c s c T BE s c T BE

ln ln ln , If ln : ) ( 2 ln : ) ( 1

2 1 2 1 2 1 2 1 2 2 2 1 1 1

= = ∂ − ∂ ⇒ = − ⇒ = =         =         =

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Temperature Variation Tolerant Biasing using VBE and VT

ature? Any temper : Question / then / / with If = ∂ ∂ ∂ ∂ ∂ ∂ − = + = T V T V T V a aV V V

ref T BE T BE ref

( )

ln(n)! for high too is 23.26 a 2 . 1 26 . 23 a V/ 2 / mV/ 086 . / mV 8 . 25 602 . 1 / 300 10 1.38 : re) temperatu (room Example

19 23

• =

= ⇒ = ⇒ − = ∂ ∂ = = ∂ ∂ = × × × =

−

V V K m T V K T V T V e V

ref BE T T T  

Silicon bandgap voltage?

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Temperature Variation Tolerant Biasing using VBE and VT - Simple Circuit

I I

( )

2 3 3 2

) ln( R R R n V V V

T BE

• ut

+ + =

You may redraw the op-amp vertically to get a better idea of the structure.

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IIT-Bombay Lecture 36 M. Shojaei Baghini

Effect of Variation of the Current with Temperature

( ) ( )

T q E V m V V kT E T V m I I T V T V T I T R n V T I T I I T I I V I I T V T V

g T BE T g T S C T BE C T C S S C C T S C T BE

− + − = − + −         = ∂ ∂ ⇒ = = ∂ ∂         ∂ ∂ − ∂ ∂ +         = ∂ ∂ 3 3 ln ) ln( 1 1 ln

2 3

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