Single-Stage Integrated- Circuit · PDF fileSingle-stage IC Amplifiers Hsin Chen, 2005 Electronics II c.f.: Microelectronic Circuits, 5th ed., Sedra/Smith 1 Single-Stage Integrated-Circuit

Single-stage IC Amplifiers

Hsin Chen, 2005

Electronics II

c.f.: Microelectronic Circuits, 5th ed., Sedra/Smith1

Single-Stage Integrated-Circuit Amplifiers


Hsin Chen, 2005

Electronics II

c.f.: Microelectronic Circuits, 5th ed., Sedra/Smith

Outline• Comparison between the MOS and the BJT• From discrete circuit to integrated circuit

- Philosophy, Biasing, …etc.• Frequency response• The Common-Source and Common-Emitter amplifier

with active loads • The Common-Gate and Common-Base amplifier

with active load• The Source and Emitter Follower• The CS and CE amplifier with source degeneration• Current mirrors with improved performance• Cascode amplifier and transistor pairings


Hsin Chen, 2005

Electronics II


6-1 Comparison between the MOS and the BJTDC characteristics

• Transconductor (iD - vGS v.s. iC - vBE )


Hsin Chen, 2005

Electronics II


• Channel-length modulation (iD - vDS ) v.s. Early effect (iC – vCE)


Hsin Chen, 2005

Electronics II


Low-frequency operation

• Transconductance

Doxnm IL

WCg ⎟⎠⎞

⎜⎝⎛= )(2 µ

T

Cm V

Ig =

• Input resistance

• Output resistance

• Intrinsic gain


Hsin Chen, 2005

Electronics II


High-frequency operation

225.1

32 and For

)(2

LVf

WLCCCC

CCgf

OVT

oxgsgdgs

gdgs

mT

πµ

π

≅

≅>>

+=

222

and For )(2

WVf

CCCCCC

gf

TT

de

mT

πµ

π

πµπ

µπ

≅

≅>>

+=

• Cutoff frequency


Hsin Chen, 2005

Electronics II


• Technology speed figure of merit v.s. Time:

• Estimated frequency performance based on scaling

Trends in IC technology


Hsin Chen, 2005

Electronics II


DC range of operation 2-3 decades of ID ∝ (VGS –VT )2

>5 decades of IC ∝ eVBE

Noise (thermal about the same) More 1/fLess 1/f

Small-signal output resistance ( ro ) Smaller for short channel

Slightly larger

Switch implementation GoodPoor

Capacitor implementation Reasonably goodVoltage dependent

MOSBJT

Cutoff frequency ( fT ) 50GHz100GHz

Comparison

From analogue or digital point of view?


Hsin Chen, 2005

Electronics II


6-2 From Discrete- to Integrated- circuitComponents

(The pictures are copied from http://140.114.23.141/htdocs/course/922_EE226002/Introduction.pdf , S.H. Hsu)


Hsin Chen, 2005

Electronics II


Hardware products

(The pictures are copied from http://140.114.23.141/htdocs/course/922_EE226002/Introduction.pdf , S.H. Hsu)


Hsin Chen, 2005

Electronics II


Design topologies

• Active load to replace R

R=?

• Current biasing

• Direct-coupled

Differential architecture to decouple DC signals (Ch7)


Hsin Chen, 2005

Electronics II


IC Biasing – current mirror (amplifier)

• Io / IREF =

• Minimum Vo =

• Effect of ro :


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Electronics II


Current steering


Hsin Chen, 2005

Electronics II


• Io / IREF =

• Minimum Vo =

• Effect of ro :β

11 ++

= mm

II

REF

O

BJT current mirror


Hsin Chen, 2005

Electronics II


6-3 Frequency response• In analysing the frequency response of circuits,capacitors 1/sC inductors sL

T(s)Vi(s) Vo(s)

01

1

01

1)(bsbs

asasasT nn

n

mm

mm

++++++

= −−

−−

L

L

Zeros :Poles :)())((

)())(()(21

21

n

mm PsPsPs

ZsZsZsasT−−−−−−

=L

L

Substituting s=jw into T(s) The gain and phase response v.s. w


Hsin Chen, 2005

Electronics II


Bode plot

0

1)(ps

sT+

=a pole

a zero0)( zssT +=

|)(| sT )(sT∠

How about positive-valued poles/zeros?


Hsin Chen, 2005

Electronics II


Example

)10/1)(10/1(10)( 52 ss

ssT++

=


Hsin Chen, 2005

Electronics II


Example- continued

)10/1)(10/1(10)( 52 ss

ssT++

=


Hsin Chen, 2005

Electronics II


High-frequency response

• Frequency response of a direct-coupled amplifier

)/1()/1)(/1()/1()/1)(/1()(

21

21

n

nH pspsps

zszszssF++++++

=L

L

We are mostly interested in 3-dB frequency, fH (or f3dB)


Hsin Chen, 2005

Electronics II


Methods to derive fH

• If a dominant pole exists1/1

1)(P

H wssF

+≅

• If not, use the cond. |F(wH)| = ½ to derive

⎟⎟⎠

⎞⎜⎜⎝

⎛+++−⎟⎟

⎠

⎞⎜⎜⎝

⎛+++≅ 22

22

122

22

1

1111111ZnZZPnPP

H wwwwwww LL

• Open-circuit time constants

∑≅

iioi

H RCw 1

Rio : resistance seen by Ci when all other Cs are open-circuit and all sources equal zeros


Hsin Chen, 2005

Electronics II


Example 6.6


Hsin Chen, 2005

Electronics II



Hsin Chen, 2005

Electronics II


Miller’s theorem – one useful technique for analysing freq response


Hsin Chen, 2005

Electronics II


Example 6.7


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Electronics II


6-4 Common-Source and Common-Emitter amplifers with acitive loads

===

o

vo

i

RAR

Common-source amplifier


Hsin Chen, 2005

Electronics II


Common-source amplifier with active load


Hsin Chen, 2005

Electronics II


• Large-signal characteristics

• Small-signal characteristics (in region III)

===

out

v

in

RAR


Hsin Chen, 2005

Electronics II


• High-frequency response

(i) Analysis by Miller’s Theorem


Hsin Chen, 2005

Electronics II


(ii) Analysis by Open-circuit time constants


Hsin Chen, 2005

Electronics II


(iii) Exact analysis


Hsin Chen, 2005

Electronics II


Formulas for Common-Emitter amplifier with active load

Documents

Single-Stage Integrated- Circuit · PDF fileSingle-stage IC Amplifiers Hsin Chen, 2005 Electronics II c.f.: Microelectronic Circuits, 5th ed., Sedra/Smith 1 Single-Stage Integrated-Circuit