applied electronic circuit
DESCRIPTION
Applied Electronic Circuit. #7 . 2007102832 김명준. Instrumentation Amplifier : IA. High Input Impedance Low Output Impedance Accurate and Stable Gain (1 ~ 1000) High CMRR . Instrumentation Amplifier : IA. 이득가변. For CMRR Tuning. Instrumentation Amplifier : IA. Differential Mode Input – - PowerPoint PPT PresentationTRANSCRIPT
1 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Applied Electronic Circuit
#7
1
2007102832 김명준
2 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Instrumentation Amplifier : IA
2
High Input Impedance
Low Output Impedance
Accurate and Stable Gain (1 ~ 1000)
High CMRR
3 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Instrumentation Amplifier : IA
3
For CMRR Tuning
+
-
O U T
v 1
v 2 +
-
O U T
R G
R 3
R 3
R 1
R 1
+
-
O U T
R 2
R 2 B
0
V o
R 2 A
이득가변𝑣𝑜=(1+2 𝑅3
𝑅𝐺) 𝑅2
𝑅1(𝑣2−𝑣1)
4 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Instrumentation Amplifier : IA
4
Differential Mode Input – Differential Mode Output Amplifier
One Chip Instrumentation Amplifier
AD620 or etc
5 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Dual OP AMP Instrumentation Amplifier
5
단점신호가 소자 통과 시 time delay 발생 !
이 에 비해 time delay 가 크다 .
→ phase distortion 발생
𝑣3=(1+ 𝑅3
𝑅4)𝑣1
𝑣𝑜=(1+ 𝑅2
𝑅1)𝑣2− 𝑅2
𝑅1𝑣3
¿ (1+ 𝑅2
𝑅1 )(𝑣2−1+
𝑅3
𝑅4
1+𝑅1
𝑅2
𝑣1)
Gain 조절 쉽지 않다
+
-
O U T V o
+
-
O U T
R 1R 2R 3R 4
0
V 1 V 2
6 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Ground loop
6
Stray capacitor
+
-
O U T
0
V o
C 1
C 2 0
R S 1
R S 2
도선 자체 저항
실제로는 도선에 연결된 Capacitor 가 아닌 매질을 통해 연결된 가상의 Capacitor
7 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Ground loop
7
𝕍1′ =
1𝑗𝑤𝐶1
𝑅𝑆1+ 1𝑗𝑤𝐶1
𝕍1
𝕍 2′ =
1𝑗𝑤𝐶2
𝑅𝑆2+ 1
𝑗𝑤𝐶2
𝕍 2
, but is possible.
𝑣𝑜≈ 𝐴𝐷𝑀 (𝑣2−𝑣1 )+ 𝐴𝐷𝑀 (𝑣2′ −𝑣1′ )+𝐴𝐶𝑀12 (𝑣2′ +𝑣1′ )
CMRR 감소의 원인
𝐶𝑀𝑅𝑅=20 log 12𝜋 𝑅𝑑𝑚𝐶𝑐𝑚
𝑅𝑑𝑚=|𝑅𝑆1−𝑅𝑆2|𝐶𝑐𝑚=
12 (𝐶1+𝐶2)
R 감소 방법 : lead wire 를 짧고 굵은 선으로 !
8 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Shield Cable
8
절연체cable
도자기 도체
절연체coaxial cable
Triaxial cable
9 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Shield
9
220V60Hz
Shield( 차폐 ) : 적절한 전압 유지
도체 ( 등전위면 )
Grounded Shield( 접지 차폐 )
Chassis
10 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Shield
10
220V60Hz
Ground Shield
Shield 가능
전원 전압에 의한 interference 제거오히려 더 나빠진다 → 원치 않는 DM current 더 생겨Leakage Current increased
𝑣𝑜𝑣 𝑠
+
-
IAShield 불가능
11 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Shield
11
Active Shield(Driven Shield)
𝑣𝑜𝑣 𝑠
+
-
IA
-+
-+
Cable 에 흐르는 전압과 같은 전압을 Shield 에 Drive
𝑣1𝑣1
𝑣2 𝑣2
12 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Shield
12
Active Shield & Ground Shield
-+
전체가 Ground Shield
13 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Transducer Bridge Amplifier
13
Resistive SensorTemperature ; Thermister, RTD
Light ; Photoresistor
Strain ; Straingage
Pressure ; piezo resistive sensor
𝑅→𝑅+∆𝑅=𝑅(1+𝛿)
𝛿=∆𝑅𝑅
물리량의 변화 -> 저항의 변화 -> 전압의 변화
14 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Bridge Circuit
14
𝑣1=𝑅2
𝑅1+𝑅2𝑣𝑅𝐸𝐹
일 때 ,
AC 사용할 수 있음Capacitive sensorInductive Sensor
𝑣2=𝑅4
𝑅3+𝑅4𝑣𝑅𝐸𝐹
→ Balanced
V R E F
R 1
R 2
R 3
R 4
V 1 V 2 V oO U T6
+3
-2
R E F5
V +7
V -4
R G 11
R G 28
R G
-V c c
V c c
15 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
15
𝔽=−𝑞𝔼=−𝑚𝕒 𝕧𝑑=𝜇𝔼
+e-
+e-
+e-
+e-
+e-
+e-
+e-
+e-
+e-
+e-
+e-
+e-
𝔼
mobility T↑,
n; 자유전자의 부피밀도전류밀도𝕁=𝑞𝑛𝜇𝔼 [ 𝐶 ∙𝑚𝑚3 ∙𝑠 ]=[ 𝐶
𝑚2 ∙𝑠 ]=[ 𝐴𝑚2 ]
conductivity
=
𝜎𝔼
16 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
16
N 개의 Free electron
𝔼
A
L
𝑛=𝑁
𝐴 ∙𝐿 [𝑚−3] T[s] 동안 L[m] 이동한다면 ,
17 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
17
¿𝜎 𝐴𝐿 𝐸𝐿=𝜎 𝐴
𝐿 𝑉
∴ 𝐼=𝜎 𝐴𝐿 𝑉
𝑉=1𝜎 ∙
𝐿𝐴 ∙ 𝐼=𝑅 ∙ 𝐼 𝑅=
1𝜎 ∙
𝐿𝐴
온도계수 (Temp wett.)
𝑇 ↑⇒𝜎 ↓⇒𝑅↑
𝑅 (𝑇 )=𝑅 (𝑇0 ) (1+𝛼𝑇 ) 𝑓𝑜𝑟 𝑃𝑡 𝑅𝑇𝐷
18 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
18
Ex. Pt RTD
𝑅 (𝑇=0℃ )=100𝛺 ,𝛼=0.00392/℃𝑅 (𝑇 )=100 (1+0.00392𝑇 )[𝛺]
𝑅 (25℃ )=109.8 [𝛺 ]
𝑅 (100℃ )=139.2[𝛺]
𝑅 (−15℃ )=94.12[𝛺 ]
𝑅+∆𝑅=𝑅 (1+∆𝑅𝑅 )
¿𝑅 (1+𝛿)
𝛿=𝛼 ∆𝑇 ∆𝑅=𝑅𝛿
19 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
19
Ex. Pt RTD
𝑣2=𝑅
𝑅+𝑅1𝑣𝑅𝐸𝐹
𝑣1=𝑅(1+𝛿)
𝑅1+𝑅(1+𝛿)𝑣𝑅𝐸𝐹
¿𝑅
𝑅+𝑅1𝑣𝑅𝐸𝐹+
𝛿
2+𝑅1
𝑅 + 𝑅𝑅1
+(1+ 𝑅𝑅1
)𝛿𝑣𝑅𝐸𝐹
𝑣𝑜=𝐴(𝑣1−𝑣2)
¿𝐴𝛿
2+𝑅1
𝑅 + 𝑅𝑅1
+(1+ 𝑅𝑅1
)𝛿𝑣𝑅𝐸𝐹
𝑖𝑓 , 𝛿≪1 ,𝑣𝑜≈𝐴 ∙𝑣𝑅𝐸𝐹
2+𝑅1
𝑅 + 𝑅𝑅1
𝛿∝𝑇
V R E F
R 1
R 1
R
V 1 V 2 V oO U T6
+3
-2
R E F5
V +7
V -4
R G 11
R G 28
R G
-V c c
V c c
(xA)
R(1+δ )
iRTD 𝑖
20 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
20
Ex. Pt RTD𝑣𝑅𝐸𝐹=15𝑉𝑅 (𝑇 )=𝑅 (1+𝛿 (𝑇 ))
¿100 (1+0.00392𝑇 )[Ω ]
𝑃 𝑅𝑇𝐷<0.2𝑚𝑊To prevent self heating
𝑃 𝑅𝑇𝐷=𝑖𝑅𝑇𝐷2 ∙𝑅
𝑖𝑅𝑇𝐷=√ 𝑃𝑅𝑇𝐷
𝑅 =√ 0.2𝑚𝑊100Ω
=1.41𝑚𝐴최종적으로 0.1V/℃ 의 출력을 얻기 위하여
T: 0~100℃ → : 0~10V
𝑖𝑅𝑇𝐷=15
𝑅1+𝑅(1+𝛿)≈ 15𝑅1
=1𝑚𝐴 Ω
margin
21 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Conduction in Metal (Conductor)
21
Ex. Pt RTD
h𝑤 𝑒𝑛𝛿≪1𝑣𝑜≈
𝐴 ∙𝑣𝑅𝐸𝐹
2+𝑅1
𝑅 + 𝑅𝑅1
𝛿∆ 𝑇=1℃
근사식이 아닌 식을 사용하면 , 근사식인 경우에 비해 약 0.26℃ 차이 발생
22 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Bridge Balancing
22
1% 저항 , 5% 전원 사용 Bridge Arm 에 흐르는 전류를 제어 → 민감도 조절
ⓐ
Balancing ( 영점 조정 )
14-16V
0-2V2mA
14V
1mA1mA
전원 : V 변동
V R E F
R 1
R 1
R
V 1 V 2 V oO U T6
+3
-2
R E F5
V +7
V -4
R G 11
R G 28
R G
-V c c
V c c
R 3
R 2
<
<
R(1+δ)
(xA)
23 김명준
Dept. of Biomed. Eng. BME303:Applied Electronic Circuit Kyung Hee Univ.
Bridge Balancing
23
To be safe,
라 가정ⓐ 점의 전압 =14V
전압 =0~2V𝑅2
2+𝑅1+𝑅= 14
1𝑚𝐴=14 𝑘Ω
에 흐르는 전류 = 2mA
𝑅3=2𝑉2𝑚𝐴=1𝑘Ω
𝑅2
2+𝑅1+𝑅= 14
1𝑚𝐴=14 𝑘Ω⇒14 𝑘Ω±140Ω
280 변화To be safe,
Choose
𝑅1=14𝑘Ω−100Ω−5002 Ω=13.65𝑘Ω
∴ h𝑐 𝑜𝑜𝑠𝑒 𝑅1=13.7𝑘Ω(∵13.65𝑘Ω𝑖𝑠 𝑛𝑜𝑡 𝑒𝑥𝑖𝑠𝑡)
𝐴=257.8𝑉 /𝑉