1. Linear OP-AMP Circuits
Chapter. 20
Linear OP-AMP Circuits
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2. 20-1 Inverting-Amplifier Circuits
① High-Impedance probe
ATT.
Input Imp. = 100㏁
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② AC-Coupled Amplifier
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10 만 10
1.59㎐
7.23㎐
10㎐
100㎑ ※ + R1 - R2
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③ Adjustable-Bandwidth Circuit
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R1//R R2
Vout
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전압이득 : constant
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9. 20-2 Noninverting-Amplifier Circuits
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In the midband
at the zero frequency
 ※ output offset voltage를 minimum으로 한다
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☆ Audio distribution Amp.
(LM348) , a quad 741
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☆ JFET-Switched Voltage Gain
(a) 0V (High Gate)
(b) VGS(off) (low Gate)
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☆ Voltage Reference
ppm (part per million) = % (10-4%)
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☆ MC1403 : 10 ppm/℃
produces a change of only 2.5㎷
for a 100℃ change in temperature
 ( 10 × percent × 100 × 2.5V )
10ppm 은  2.5㎷/100℃
2.5V
MC1403
: (10×0.0001%×100×2.5)/100℃
4.5V~40V
special fuction IC
10 × ×2.5V
= 10-3×2.5V=2.5㎷/100℃
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15. 20-3 Inverter/Noninverter Circuits
① Switchable Inverter/Noninverter (Reversible voltage gain)
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① Top position
② Bottom position
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② JFET-Controlled switchable Inverter
VGS(off) : Low Gate :
JFET + -
0V : High Gate :
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③ Inverter with adjustable Gain
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④ Sign Changer
(i) wiper  to the right (GND)
(ii) wiper  to the left
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⑤ Adjustable and reversible Gain
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(i) wiper  to the right (GND)
(ii) wiper  to the left + -
adjustable nR 
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☆ Phase Shifter
0˚~180˚
① for f<<fc  capacitor is open
 phase “0˚”
② Av=ACL of inverting ch.
for f>>fc  capacitor is short
∴ overall Gain (-180˚)
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23. Mobile Communication Lab. (http://mobile pknu.ac.kr)1㎑
Av=2 Xc
② R=10㏀  fc=723㎐
③ R=100㏀  fc=72.3㎐
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24. 20-4 Differential Amplifiers
<Basic Differential Amp.>
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25. Mobile Communication Lab. (http://mobile pknu.ac.kr)1) 2)
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∴ noninverting input V2’는
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<CMRR of external resistors>
앞에서 이면
V1=V2 가 되어
가 된다.
그러나 실제 Resistor의 tolerence 때문에,
R1≠R1’ , R2≠R2’ 가 되어서,
-----①
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V2’ +
Vout ② - R2
※ noninverting voltage gain 은 R1 ③ ④
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①식에 ②,③,④을 代入
: tolerence of the
resistance
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<Calculating CMRR>
tolerance
 54㏈
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<buffered inputs>
 isolate
앞 차동증폭기에서 입력 저항 R1과 R1’는 전압이득변화와
CMRR를 감소시킨다. 따라서 入力 Impedance를 증가 시키면
된다.
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<Wheatstone Bridge>
이면 정상
그러나 저항의 오차 (tolerance= )
때문에 오차전압 발생
그림에서 R2와 R4에 걸리는 전압이
같으면 Vout=0
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34. Mobile Communication Lab. (http://mobile pknu.ac.kr)
<Transducers> : 변환기
상기 wheastone bridge를 이용, 그리고 Diff. Amp.를 이
용하여 계측 증폭기 설계한다.
transducer 의 성질(특징)을 갖는
wheastone bridge 회로 +
Diff. Amp.
 Instrumentation amp.
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35. Mobile Communication Lab. (http://mobile pknu.ac.kr)
Transducers ?
input transducers (비전기량  전기량)
- photoresistor (light  resistance)
- thermistor (temperature  resistance)
(2) output transducer (전기량  비전기량)
- LED (current  light)
- Speaker (voltage  soundwave)
※ wheastone bridge ?
: nonelectrical quantitics을 측량하는데 사용되는
transducer 이다.
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§. A Typical Application
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37. Mobile Communication Lab. (http://mobile pknu.ac.kr)① ②
또한 Diff. Amp. 의 이다.
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38. Mobile Communication Lab. (http://mobile pknu.ac.kr)
∴ 여기서 ※
또한,
 88㏈
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39. 20-5 Instrumentation Amplifiers
 dc 성능이 최적화된 a differential Amp.
high input Impedance
large voltage gain
a high CMRR
low input offsets
low temperature drift
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preamp
Diff amp.
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☆ preamp 단
; 각 단자인 noninverting 단자에 각각 동산신호입력을
가했을 때, 각 op Amp. 出力은 같다.
따라서 R1,R2을 포함하는 각 저항 단자에는 같은 전압이 나타난다.
즉, A점은 virtual GND (Floating)
따라서, input OP Amp. 은 voltage follower
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☆ Diff. Amp. 단
따라서 Total ACM은,
R1+ R1대신 분리 되지 않는 RG 저항이라면,
여기서,
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43. Mobile Communication Lab. (http://mobile pknu.ac.kr)
<§. Guard driving>
▶ Shielded Cable : a bridge로 부터의 차동신호(differential signal)가
작기 때문에 전자파 간섭으로 부터 신호전송을 분
리 시키기 위해
단일칩 IC
그러나  ◎ leakage current 및 회로의 Capacitance를 증가시킴.
 transducer 저항치를 변화시킴.
-. low input bias
-. offset current
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▶ guard driving : Fig 20-19
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<§. Intergrated Instrumentation Amp.>
: Monolithic Inst. (계측증폭기)
Rg를 제외하는 계측 Amp을 IC 化
AD620
light amplification by stimulated emission of radiation Rg
laser trimming
: 정확한 저항 값을 얻기 위해 laser를 갖는
반도체 chip상에 저항영역을 없앰을 의미
pin 2,3 : input
4,7 : supply voltage
6 : output
5 : GND
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46. Mobile Communication Lab. (http://mobile pknu.ac.kr)
- Monolithic 계측 Amp.
voltage gain : 1~1000
외부저항
CMRR : 100㏈
입력 Impedance 100㏁
입력 offset voltage 0.1㎷ 이하
drift 0.5㎶/℃
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47. 20-6 Summing Amplifier Circuits
※ The Subtracter (감산기)
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48. Mobile Communication Lab. (http://mobile pknu.ac.kr)
※ Summing on Both inputs
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49. Mobile Communication Lab. (http://mobile pknu.ac.kr)RF + -
R1//R2
V3’
or V4’
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50. Mobile Communication Lab. (http://mobile pknu.ac.kr)
※ The Averager
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51. Mobile Communication Lab. (http://mobile pknu.ac.kr)
※ D/A Converter
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52. Mobile Communication Lab. (http://mobile pknu.ac.kr)
4 digital input  16 possible input combinations
‥‥‥ 1111
Vout=0
Vout=-0.25
Vout=-1.875
Vout=-0.125
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53. Mobile Communication Lab. (http://mobile pknu.ac.kr)
20-7 Current Boosters
통상 OP Amp.의 단락 출력 전류로 25㎃ 이하
Power OP Amp. LM675, LM12  3~10A
① Unidirectional booster
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54. Mobile Communication Lab. (http://mobile pknu.ac.kr)
: short-circuit output current
of OP Amp.  25㎃
- NFB 이므로
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55. Mobile Communication Lab. (http://mobile pknu.ac.kr)
② Bidirectional current booster
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56. 20-8 Voltage–Controlled Current Sources
※ Floating load (전압제어 전류원) : VCIS
비 반전입력이 반전입력에 boostrapping.
따라서 R 양단에 Vin이 나타난다.
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57. Mobile Communication Lab. (http://mobile pknu.ac.kr)- -
ex) 
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58. Mobile Communication Lab. (http://mobile pknu.ac.kr)
※ Grounded load
최대 출력 전류를 크게 해준다.
OP Amp.의 최대 출력 전류보다 적도록 설계, 즉 10~25㎃
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59. Mobile Communication Lab. (http://mobile pknu.ac.kr)※
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60. Mobile Communication Lab. (http://mobile pknu.ac.kr)
< Output Current Directly proportional to input voltage>
boostrapping
ie1 VR
iout
ie1
위 그림은 入力 전압이 증가하면 출력 전류가 감소
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61. Mobile Communication Lab. (http://mobile pknu.ac.kr)
θ1의 emitter current
(θ1의 collector 저항 R 양단에 걸리는 전압)
∴ A point 전압은 : 
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62. Mobile Communication Lab. (http://mobile pknu.ac.kr)- - -
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63. Mobile Communication Lab. (http://mobile pknu.ac.kr)
<※ Howland Current Source>
if, it needs a bidirectional current
iout/2
Vout
iout
iout/2
<bidirectional VCIS>
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64. Mobile Communication Lab. (http://mobile pknu.ac.kr)
- if load current 가 zero 보다 크면
noninverting input 는 GND가 아니고,
inverting input 도 더 이상 virtual GND가 아님
∴ 따라서 noninverting input voltage는 load 저항 단자에
걸리는 전압과 같다.
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65. Mobile Communication Lab. (http://mobile pknu.ac.kr)- - -
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66. 20-9 Automatic Gain Control
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67. Mobile Communication Lab. (http://mobile pknu.ac.kr)
① peak to peak output voltage < 1.4 Vpp
θ2  cutoff, C2는 uncharge  θ1의 gate는 –VEE
; 충분한 (-) 전압이면 θ1도 cutoff. 또 rds가 크게된다.
※  이것은 최대 입력 전압이 비 반전 단자에 가해진다는 의미
 비반전 증폭기
② output voltage > 1.4 Vpp
θ2 on  C2 charge  gate voltage 증가  rds감소
비반전 전압이 분배되어 작은 입력전압으로  전압이득 감소
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For small-signal operation with drain voltages near zero,
☆ JFET (θ1) operates in the ohmic region, rds to ac signals
이 rds 저항은 gate voltage로서 controll 된다.
: The more negative the gate voltage is the larger rds becomes
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69. Mobile Communication Lab. (http://mobile pknu.ac.kr)+ - R1
Vin
Vin’ R3
rds
Vout
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70. Mobile Communication Lab. (http://mobile pknu.ac.kr)
<Low-level video AGC>
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71. Mobile Communication Lab. (http://mobile pknu.ac.kr)
- JFET : voltage controlled resistance
① VAGC = 0V  JFET의 Gate는 negative bias, cutoff
 rds는 maximum
② VAGC 가 증가  rds는 감소  入力 전압 감소
 VAGC 전압이 전체 전압이득을 조절
- Inverting Amp.
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72. Mobile Communication Lab. (http://mobile pknu.ac.kr)
( Inverting Amp.)
※ 입력 신호 100㎷ 까지에 대하여 잘 동작
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< High-Level video AGC >
JFET  LED-photoresistor
(R7 : 빛이 증가하면 감소)
∴ VAGC(大)  빛의 양 大  R7 감소
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※ 10V 입력신호의 높은 level 에까지 잘동작
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75. 20-10 Single-Supply operation
(power supply의 ripple, noise 제거 역할)
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[1] ◎ dc 등가회로적으로는, 모든 C가 open되고, 또 noninverting input
은 +0.5VCC 이며 voltage follower이므로 dc output voltage는
+0.5VCC이다.
◎ Inverting input은 대략 +0.5VCC에 해당
◎ Input offsets은 minimized 된다. (∵ voltage gain is unity)
[2] AC 회로 -
- noninverting input (power supply)의 ripple 주파수보다 f3 주파수가
훨씬 작아야 한다.
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77. Mobile Communication Lab. (http://mobile pknu.ac.kr)
<Noninverting Amp.>
○ for maximum output swing voltage
: noninverting input 가 가 되도록
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78. Mobile Communication Lab. (http://mobile pknu.ac.kr)
DC 회로적으로 : 모든 C open
 voltage gain 1
 output offset voltage를 최소화
 dc output voltage 는 C2에서 차단된다.
(2) AC 회로
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