Gunma University Kobayashi Lab
Design of Operational Amplifier Phase Margin
Using Routh-Hurwitz Method
ICMEMIS2018
Nov.4-Nov.6 2018
ID:IPS3-05
JianLong Wang,
Nobukazu Tsukiji, Haruo Kobayashi
Kobayashi Lab, Gunma University
2/39
Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
3/39
Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
4/39
Research Background (Stability Theory)
2018/11/7
โ Electronic Circuit Design Field
- Bode plot (>90% frequently used)
- Nyquist plot
โ Control Theory Field
- Bode plot
- Nyquist plot
- Nicholas plot
- Routh-Hurwitz stability criterion
Very popular in control theory field
but rarely seen in electronic circuit books/papers
- Lyapunov function method
:
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Electronic Circuit Text Book
2018/11/7
We were NOT able to find out any electronic circuit text book
which describes Routh-Hurwitz method
for operational amplifier stability analysis and design !
None of the above describes Routh-Hurwitz.
Only Bode plot is used.
Razavi Gray Maloberti Martin
6/39
Control Theory Text Book
2018/11/7
Most of control theory text books
describe Routh-Hurwitz method
for system stability analysis and design !
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Research Objective
Our proposal
For
Analysis and design of operational amplifier
stability and phase margin
Use
Routh-Hurwitz stability criterion
We can obtain
โข Explicit stability condition for circuit parameters
(which can NOT be obtained only with Bode plot).
โข Relationship between R-H parameters and phase
margin2018/11/7
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
Nyquist plot
Bode plot
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Nyquist plot
โข If the open-loop system is stable(P=0),
the Nyquist plot mustnโt encircle the point (-1,j0).
Nyquist plot of open-loop system
j
๐1,2 โ โ
๐1 = 0 ๐2 = 0โ1 0
๐พ2๐พ1โข Open-loop frequency characteristic
Closed-loop stability
โข Necessary and sufficient condition :
When ๐ = 0 โโ, ๐ = ๐ โ ๐
N : number, Nyquist plot anti-clockwise encircle point (-1,j0).
P: number, positive roots of open-loop characteristic equation.
๐0
โ ๐บ๐๐๐๐ ๐๐0 = โ๐, ๐บ๐๐๐๐(๐๐0) < 1
Z: number, positive roots of closed-loop characteristic equation.
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Bode Plot
2018/11/7
1
0
๐
๐
โ1800
๐บ๐
P๐
๐บ๐ precedes P๐
Greater spacing between ๐บ๐ and P๐
More stable
๐1
๐๐
๐๐ด(๐๐)
โ ๐๐ด(๐๐)
Phase margin : PM = 1800 + โ ๐๐ด ๐ = ๐1
๐1: gain crossover frequency
Bode plot is useful,
but it does NOT show explicit stability conditions of circuit parameters.
๏ผgain crossover point๏ผ
๏ผphase crossover point๏ผ
Feedback system is stable
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Phase Margin and Gain Margin
2018/11/7
j
๐ = โ๐๐
๐๐
โ ๐๐ด(๐๐๐)
(โ1, ๐0)
๐ 0
๐บ(๐๐)
โ
๐
โ0dB
0o
โ1800
๐(log ๐ ๐๐๐๐)
๐(log ๐ ๐๐๐๐)
20๐๐๐ ๐๐ด(๐๐)
โ ๐๐ด(๐๐)
๐๐๐๐
โ: Gain Margin
๐: Phase Margin
Fig.(a) Nyquist plot
Fig.(b) Bode Plot
โข The included angle
Intersection point at ๐๐
Negative real axis
โข The angle difference
โ1800
Phase at ๐๐
โข Reciprocal 1
๐บ(๐๐)
โข The distance
0dB, real axis
Gian at ๐๐
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
13/39
Routh Stability Criterion
Characteristic equation:
๐ท ๐ = ๐ผ๐๐ ๐ + ๐ผ๐โ1๐ ๐โ1 + โฏ + ๐ผ1s + ๐ผ0 = 0
Sufficient and necessary
condition:
(i) ๐ผ๐ > 0 for ๐ = 0,1, โฆ , ๐
(ii) All values of Routh tableโs
first columns are positive.
๐๐
๐๐โ1
๐๐โ2
๐๐โ3
๐0
โฎ โฎ โฎโฎโฎโฎ
๐ผ๐
๐ผ๐โ1
๐ผ๐โ2
๐ผ๐โ3
๐ผ๐โ4
๐ผ๐โ5
๐ผ๐โ6
๐ผ๐โ7
โฏ
โฏ
โฏ
โฏ๐ฝ1 =๐ผ๐โ1๐ผ๐โ2 โ ๐ผ๐๐ผ๐โ3
๐ผ๐โ1๐ฝ2 =
๐ผ๐โ1๐ผ๐โ4 โ ๐ผ๐๐ผ๐โ5
๐ผ๐โ1
๐พ1 =๐ฝ1๐ผ๐โ3 โ ๐ผ๐โ1๐ฝ2
๐ฝ1
๐พ2 =๐ฝ1๐ผ๐โ5 โ ๐ผ๐โ1๐ฝ3
๐ฝ1
๐ผ0
๐ฝ3 ๐ฝ4
๐พ3 ๐พ4
Routh table
Mathematical test
Determine whether given polynomial has all roots in the left-half plane.
&
2018/11/7
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
15/39
Four Examples
2018/11/7
Ex.1 ๐บ ๐ =๐พ
1 + ๐1๐ + ๐2๐ 2 + ๐3๐ 3
๐บ ๐ =๐พ(1 + ๐1๐ )
1 + ๐1๐ + ๐2๐ 2Ex.2
๐บ ๐ =๐พ(1 + ๐1๐ )
1 + ๐1๐ + ๐2๐ 2 + ๐3๐ 3Ex.3
๐บ ๐ =๐พ(1 + ๐1๐ + ๐2๐ 2)
1 + ๐1๐ + ๐2๐ 2 + ๐3๐ 3Ex.4
Zero Zero Point, Three Pole Points
One Zero Point, Two Pole Points
One Zero Point, Three Pole Points
Two Zero Points, Three Pole Points
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Based on Routh-Hurwitz Criterion
G(๐ )+
โ
๐ถ(๐ )๐ (๐ )
๐บ ๐ =๐พ(1 + ๐๐ )
1 + ๐1๐ + ๐2๐ 2 + ๐3๐ 3
๐ป ๐ =๐บ(๐ )
1 + ๐บ(๐ )=
๐พ + ๐พ๐๐
1 + ๐พ + (๐1+๐พ๐)๐ + ๐2๐ 2 + ๐3๐ 3
Open-loop transfer function:
Closed-loop transfer function:
Based on Routh-Hurwitz criterion:
๐3
๐2
๐1
๐3
๐0
๐2
๐1 + ๐พ๐
1 + ๐พ
1 + ๐พ
๐2(๐1 + ๐พ๐) โ ๐3(1 + ๐พ)
๐2
๐3 > 0 ๐2 > 0
1 + ๐พ > 0
๐พ >๐3 โ ๐1๐2
๐2๐ โ ๐3
Example 3
๐2(๐1 + ๐พ๐) โ ๐3(1 + ๐พ)
๐2> 0
Routh table
๐พ <๐3 โ ๐1๐2
๐2๐ โ ๐3
At condition:๐2๐ โ ๐3 > 0
At condition:๐2๐ โ ๐3 < 02018/11/7
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Based on Nyquist Criterion
๐บ ๐๐ =๐พ(1 + ๐๐๐)
1 โ ๐2๐2 + ๐(๐1๐ โ ๐3๐3)=
๐พ[ 1 โ ๐2๐2 + ๐1๐๐2 โ ๐3๐๐4 + ๐ ๐๐ โ ๐2๐๐3 โ ๐1๐ + ๐3๐3 ]
(1 โ ๐2๐2)2 + (๐1๐ โ ๐3๐3)2
๐
๐ = 0
๐ = โ
sketch chart of Nyquist plot
.(โ1, ๐0)
๐ด.
๐๐ โ ๐2๐๐3 โ ๐1๐ + ๐3๐3 = 0
At point A๐2 =๐1 โ ๐
๐3 โ ๐2๐
Special frequency expressions
๐บ ๐๐ =๐พ(1 โ ๐2๐2 + ๐1๐๐2 โ ๐3๐๐4)
(1 โ ๐2๐2)2 + (๐1๐ โ ๐3๐3)2= ๐พ
๐3 โ ๐2๐
๐3 โ ๐1๐2
Frequency domain:
โ ๐บ ๐๐ = โ๐
Stability condition:
๐บ ๐๐ < 1
๐3 โ ๐1๐2
๐2๐ โ ๐3< ๐พ <
๐3 โ ๐1๐2
๐3 โ ๐2๐
At condition: (๐3โ๐1๐2)(๐3 โ ๐2๐) < 0
At condition: (๐3โ๐1๐2)(๐3 โ ๐2๐) > 0
๐3 โ ๐1๐2
๐3 โ ๐2๐< ๐พ <
๐3 โ ๐1๐2
๐2๐ โ ๐3
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Ex.1: Two-stage amplifier with C compensation
Ex.2: Two-stage amplifier with C, R compensation
Simulation Verification
Discussion & Conclusion
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Amplifier 1
๐1 = ๐ 1๐ถ1 + ๐ 2๐ถ2 +(๐ 1 + ๐ 2 + ๐ 1๐บ๐2๐ 2)๐ถ๐ ๐2 = ๐ 1๐ 2(๐ถ1๐ถ2 + ๐ถ1๐ถ๐ + ๐ถ2๐ถ๐)
๐1 = โ๐ถ๐
๐บ๐2
๐ด0 = ๐บ๐1๐บ๐2๐ 1๐ 2
Open-loop transfer function from small signal model
๐ด ๐ =๐ฃ๐๐ข๐ก(๐ )
๐ฃ๐๐(๐ )= ๐ด0
1 + ๐1๐
1 + ๐1๐ + ๐2๐ 2
Fig.1 Two-stage amplifier with inter-stage capacitance
๐ฃ๐๐ถ๐1
๐ฃ๐ ๐1 ๐2
๐3 ๐4
๐๐๐๐๐ 3
๐๐๐๐๐ 4
M6T
M6B M8B
M8T
๐ฃ๐๐ข๐ก
๐ถ๐ฟ
๐๐ท๐ท ๐๐ท๐ท ๐๐ท๐ท
๐7โ
โกโ
โ
โ
โ๐ถ1 ๐ถ2๐ 1
๐ 2
๐บ๐2๐1
๐บ๐1๐ฃ๐๐
๐ฃ๐๐ข๐ก
๐ถ๐1โ โก
+
โ
Transistor level circuit
Small-signal model
๐ฃ๐๐ = ๐ฃ๐ โ ๐ฃ๐
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Routh-Hurwitz method
๐๐๐ข๐ก(๐ )
๐๐๐(๐ )=
๐ด(๐ )
1 + ๐๐ด(๐ )=
๐ด0(1 + ๐1๐ )
1 + ๐๐ด0 + ๐1 + ๐๐ด0๐1 ๐ + ๐2๐ 2
๐ = ๐1 + ๐๐ด0๐1
= ๐ 1๐ถ1 + ๐ 2๐ถ2+ ๐ 1 + ๐ 2 ๐ถ๐ + ๐บ๐2 โ ๐๐บ๐1 ๐ 1๐ 2๐ถ๐ > 0
Closed-loop transfer function:
Explicit stability condition of parameters:
๐ 1 = ๐๐๐||๐๐๐ = 111๐ฮฉ
๐ 2 = ๐๐๐||๐ ๐๐๐๐ ๐ โ ๐๐๐ = 333๐ฮฉ
๐บ๐1 = ๐๐๐ = 100 ฮค๐ข๐ด ๐
๐บ๐2 = ๐๐๐ = 180 ฮค๐ข๐ด ๐
๐ถ1 = ๐ถ๐๐4 + ๐ถ๐๐2 + ๐ถ๐๐ 7 = 13.6๐๐น
๐ถ2 = ๐ถ๐ฟ + ๐ถ๐๐8 โ ๐ถ๐ฟ + 1.56๐๐น
= 101.56๐๐น (๐ถ๐ฟ = 100๐๐น)
Short-channel CMOS parameters:
๐ด(๐ )+
โ
๐๐๐ข๐ก(๐ )๐๐๐(๐ )
๐
Relationship: ๐ and phase margin
MATLAB
Data fitting
๐: time dimension parameter
Closed-loop configuration
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Data Processing by MATLAB
2018/11/7
โข Data collection: [GM, PM, ๐น๐๐, ๐น๐๐]=margin(G)
โข Data fitting๏ผ p=polyfit(x,y,n) Curve Fitting Tool
๐=0.01
๐ถ๐1 [fF] 10 20 30 40 50 60 70 80 90 โฆ
ฮธ [uS] 0.11 0.18 0.25 0.32 0.39 0.46 0.53 0.60 0.67 โฆ
PM [degree] 16 19 22 24 27 29 31 33 34 โฆ
GM [dB] 9.1 7.6 7.0 6.6 6.4 6.3 6.2 6.0 6.0 โฆ
๐นg๐ [GHz] 4.5 3.4 2.9 2.6 2.3 2.1 2.0 1.9 1.8 โฆ
๐น๐๐ [GHz] 2.6 2.1 1.8 1.5 1.4 1.2 1.1 1.0 9.4 โฆ
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Data Fitting Result
Fig.2 Relationship between PM and parameter ฮธ at various feedback factor conditions.
โข One-to-one relationship
โข increase of parameterโs value
phase margin will be increased
feedback system will be more stable
Fitted Curve
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๐ =0.01 Conditionใ ใ๐in
๐๐๐ข๐ก+-
๐ 1
๐ 2
โ
โ๐ด(๐ )
๐ =๐ 2
๐ 1 + ๐ 2
PM= ๐1 ๐= 2.601๐28๐5 โ 5.616๐23๐4 + 4.683๐18๐3
โ 1.915๐13๐2 + 4.076๐28๐ + 13.38
ฮธ: independent variable
๐๐: dependent variable
Fig.3 Relationship between PM with parameter ฮธ at feedback factor ๐ = 0.01 condition.
Curve Fitting Tool
Relation function:
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Amplifier 2
Fig.4 Two-pole amplifier with compensation network using a nulling resistor
๐ฃ๐๐ถ๐2
๐ฃ๐ ๐1 ๐2
๐3 ๐4
๐๐๐๐๐ 3
๐๐๐๐๐ 4
M6T
M6B M8B
M8T
๐ฃ๐๐ข๐ก
๐ถ๐ฟ
๐๐ท๐ท ๐๐ท๐ท ๐๐ท๐ท
๐7โ
โกโโ
โ
๐ถ1 ๐ถ2๐ 1
๐ 2
๐บ๐2๐1
๐บ๐1๐ฃ๐๐
๐ฃ๐๐ข๐ก
๐ถ๐2โ โก
+
โ
๐ ๐
๐ ๐
(a) Transistor level circuit
(b) Small-signal model
โ
Open-loop transfer function:
๐ด ๐ =๐ฃ๐๐ข๐ก(๐ )
๐ฃ๐๐(๐ )= ๐ด0
1 + ๐1๐
1 + ๐1๐ + ๐2๐ 2 + ๐3๐ 3
๐1 = โ๐ถ๐
๐บ๐2โ ๐ ๐๐ถ๐
๐ด0= ๐บ๐1๐บ๐2๐ 1๐ 2 ๐1 = ๐ 1๐ถ1 + ๐ 2๐ถ2 + (๐ 1 + ๐ 2 + ๐ ๐ + ๐ 1 ๐ 2๐บ๐2)๐ถ๐
๐2 = ๐ 1๐ 2(๐ถ2๐ถ๐ + ๐ถ1๐ถ2 + ๐ถ1๐ถ๐) +๐ ๐๐ถ๐(๐ 1๐ถ1 + ๐ 2๐ถ2) ๐ฃ๐๐ = ๐ฃ๐ โ ๐ฃ๐2018/11/7
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Routh-Hurwitz Method
Closed-loop transfer function:
๐๐๐ข๐ก(๐ )
๐๐๐(๐ )=
๐ด(๐ )
1 + ๐๐ด(๐ )=
๐ด0(1 + ๐1๐ )
1 + ๐๐ด0 + ๐1 + ๐๐ด0๐1 ๐ + ๐2๐ 2 + ๐3๐ 3
๐ผ = ๐1 + ๐๐ด0๐1
= ๐ 1๐ถ1 + ๐ 2๐ถ2+ ๐ 1 + ๐ 2 + ๐ ๐ ๐ถ๐ + ๐บ๐2 โ ๐๐บ๐1 + ๐๐บ๐1๐บ๐2๐ ๐ ๐ 1๐ 2๐ถ๐ > 0
ใ ใ๐in๐๐๐ข๐ก+
-๐ 1
๐ 2
โ
โ๐ด(๐ )
๐ =๐ 2
๐ 1 + ๐ 2
๐ฝ =๐1 + ๐๐ด0๐1 ๐2 โ ๐3(1 + ๐๐ด0)
๐2> 0
(๐๐๐๐๐๐๐ก๐๐ ๐๐ ๐ ๐๐ข๐กโ ๐ ๐ก๐๐๐๐)
Relationship:๐ผ๏ผ๐ฝand phase margin
Interpolation by MATLAB
๐ผ, ๐ฝ: time dimension parameters
Explicit stability condition of parameters:
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Data Collection
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๐ถ๐1
๐ ๐11
๐ ๐12
๐ ๐13
โฆ
๐ ๐19
(๐ผ11, ๐ฝ11)
(๐ผ12, ๐ฝ12)
(๐ผ13, ๐ฝ13)
(๐ผ19, ๐ฝ19)
โฆ
๐ ๐21
๐ ๐22
๐ ๐23
โฆ
๐ ๐29
(๐ผ21, ๐ฝ21)
(๐ผ22, ๐ฝ22)
(๐ผ23, ๐ฝ23)
(๐ผ29, ๐ฝ29)
โฆ
๐ถ๐2
๐ ๐31
๐ ๐32
๐ ๐33
โฆ
๐ ๐39
(๐ผ31, ๐ฝ31)
(๐ผ32, ๐ฝ32)
(๐ผ33, ๐ฝ33)
(๐ผ39, ๐ฝ39)
โฆ
๐ถ๐3 โฆ
๐ ๐91
๐ ๐92
๐ ๐93
โฆ
๐ ๐99
(๐ผ91, ๐ฝ91)
(๐ผ92, ๐ฝ92)
(๐ผ93, ๐ฝ93)
(๐ผ99, ๐ฝ99)
โฆ
๐ถ๐9
Produce 9 โ 9 = 81 groups data
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Interpolation by MATLAB
2018/11/7
Fig.5 Relationship between PM with parameter ๐ผ1, ๐ฝ1
at feedback factor ๐ = 0.01 condition.
โข Linear relationship
โข increase of parameterโs value
phase margin will be increased
feedback system will be more stable
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
29/39
Verification Circuit
๐ฃ๐๐๐๐ถ๐1
๐ฃ๐๐๐ ๐1 ๐2
๐3 ๐4
๐ฃ๐๐ข๐ก
๐ถ๐ฟ
๐๐๐
๐8โ
โกโ
โ
โ
โ๐ถ1 ๐ถ2๐ 1
๐ 2
๐บ๐2๐1
๐บ๐1๐ฃ๐๐
๐ฃ๐๐ข๐ก
๐ถ๐1โ โก
+
โ
๐๐ท๐ท
ใ ใ๐in๐๐๐ข๐ก+
-9.9๐
0.1๐โ
โ๐ด(๐ )
๐ =0.1
0.1 + 9.9= 0.01
๐7๐6๐5
(a) Transistor level circuit
(b) Small-signal model
Fig.6 Two-pole amplifier with inter-stage capacitance
๐๐๐ข๐ก(๐ )
๐๐๐(๐ )=
๐ด(๐ )
1 + ๐๐ด(๐ )=
๐ด0(1 + ๐1๐ )
1 + ๐๐ด0 + ๐1 + ๐๐ด0๐1 ๐ + ๐2๐ 2
๐ = ๐1 + ๐๐ด0๐1
= ๐ 1๐ถ1 + ๐ 2๐ถ2+ ๐ 1 + ๐ 2 ๐ถ๐1 + ๐บ๐2 โ ๐๐บ๐1 ๐ 1๐ 2๐ถ๐1 > 0
Closed-loop transfer function:
Explicit stability condition of parameters:
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Data Fitting by MATLAB
Fig.7 Relationship between PM with compensation capacitor ๐ถ๐1
at variation feedback factor ๐ conditions.
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PM versus ๐ถ๐1
๐ = 0.01 condition ใ ใ๐in๐๐๐ข๐ก+
-๐ 1
๐ 2
โ
โ๐ด(๐ )
๐ =๐ 2
๐ 1 + ๐ 2= 0.01
PM= ๐1 ๐ถ๐1
= โ1.026๐36๐ถ๐13 + 1.52๐24๐ถ๐1
2 + 4.488๐12๐ถ๐1 + 7.247
Relation function:
๐ถ๐1: independent variable
๐๐: dependent variable
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๐ถ๐1versus PM
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๐ = 0.01 condition ใ ใ๐in๐๐๐ข๐ก+
-๐ 1
๐ 2
โ
โ๐ด(๐ )
๐ =๐ 2
๐ 1 + ๐ 2= 0.01
๐ถ๐1 = ๐1 ๐๐= 6.343๐โ15๐๐3 โ 2.091๐โ13๐๐2 + 2.493๐โ12๐๐ โ 9.822๐โ12
Relation function:
๐ถ๐1: dependent variable
๐๐: independent variable
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Practicability
For stable feedback system,
necessary PM value: 45 degree or 60 degree
PM=๏ผ๏ผdegree, ๐ถ๐1 = 2.5694๐โ10๐น = 0.25694nF
PM=60degree, ๐ถ๐1 = 7.5709๐โ10๐น = 0.75709nF
For stability and needed PM value,
compensation capacitance can be calculated.
๐ถ๐1 = ๐1 ๐๐= 6.343๐โ15๐๐3 โ 2.091๐โ13๐๐2 + 2.493๐โ12๐๐ โ 9.822๐โ12
2018/11/7
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Simulation by LTspice
feedback factor:
๐ =0.1๐
9.9๐= 0.01compensation capacitor:
๐ถ๐1 = 0.25694๐๐น
2018/11/7
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Simulation Result
2018/11/7๐โ๐๐ ๐ ๐๐๐๐๐๐ = 180ยฐ โ 133ยฐ = 47ยฐ
133ยฐ
Phase[d
egre
e]
Gain
Frequency
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Contents
2018/11/7
Research Objective & Background
Stability Criteria
- Nyquist Criterion
- Routh-Hurwitz Criterion
Equivalence at Mathematical Foundations
Relationship between R-H parameters and phase margin
Simulation Verification
Discussion & Conclusion
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Discussion
Depict small signal equivalent circuit of amplifier
Derive open-loop transfer function
Derive closed-loop transfer function
& obtain characteristics equation
Apply R-H stability criterion
& obtain explicit stability condition
Especially effective for
Multi-stage opamp (high-order system)
Limitation
Explicit transfer function with polynomials of ๐ has to be derived.2018/11/7
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Conclusion
โข R-H method, explicit circuit parameter conditions can
be obtained for feedback stability.
โข Equivalency of their mathematical foundations
was shown
โข Relationship between R-H criterion parameter with PM:
- linear relationship
- the system will be more stable, following with the
increase of parameterโs value.
โข The proposed method has been confirmed with LTspice
simulation
R-H method can be used
with conventional Bode plot method.2018/11/7
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2018/11/7
Thank you
for your kind attention.
Dr. Yuji Gendai is acknowledged
for his suggestions and helpful comments