Biopotential Ampliiers Hsiao-Lung Chan, Ph.D. Dept Electrical Engineering Chang Gung University, Taiwan chanhl@mail.cgu.edu.tw
Operational ampliier Practical Ideal Biopotential ampliiers
Ideal vs. practical OP amp Biopotential ampliiers 3
Dierential- and common-mode inputs V o = A d V d + A cm V cm where A d = A ol open-loop gain Ideally, A d =, A cm = CM = log A d A cm = or, = A d A cm Biopotential ampliiers 4
Inverting ampliier V o V i = - F I Ideally, in = I and out = Biopotential ampliiers 5
Inverting ampliier Biopotential ampliiers 6
Noninverting ampliier V o V i = + Ideally, Z i = and Z o = Biopotential ampliiers 7
Dierential Ampliier id V V 3 - + Vo id = + 3 4 V o 4 V V 3 4 V V i 4 3 Biopotential ampliiers 8
Dierential Ampliier: Imbalance Eect Vcm + - - + + - - Vdm Vdm -ε - + Vo V o V o V V dm cm V V dm cm A dm V dm A cm V cm A dm, A cm CM log A A dm cm log Biopotential ampliiers 9
Instrumental Ampliier IA Three OP-AMP IA ealization V + id id = V g - - + ' ' - + V o Vo ' V V g Biopotential ampliiers
Analog ilters S. Franco, Design with Operational Ampliiers and Analog Integrated Circuits, Second Edition, 998. Biopotential ampliiers
Biopotential ampliiers First-order lowpass active ilter j H j H sc V V s H in O H and C where
Biopotential ampliiers 3 First-order lowpass ilter Vi + - Vo C j H j H sc V V s H i O H and C where
Biopotential ampliiers 4 First-order highpass ilter H and C where sc sc V V s H in O j j H j H
Biopotential ampliiers 5 First-order highpass ilter j j H j H sc sc V V s H i O H and C where Vo - Vi + C
First-order bandpass active ilter C Vi C - + Vo log H db - dbdecade H s V V O i sc sc sc H j [ j j ][ j ] where C and C Biopotential ampliiers 6
Instrumental ampliier with irst-order highpass ilter V + - ' - Vo V g - + ' + Vre Integrator eedback C - + V o s G V V s C Biopotential ampliiers 7
Biopotential ampliiers 8 Second-order ilters s Q s n s n s n s H Low-pass response n = n =, n = ω s Q s s H Q j j H High-pass response n =, n = n = s Q s s s H Q j j H
Second-order ilters Low-pass response High-pass response S. Franco, Design with Operational Ampliiers and Analog Integrated Circuits, Second Edition, 998. Biopotential ampliiers 9
Second-order Sallen-Key lowpass ilter nc - Vi m + Vo C H j j Q where mnc and Q mn m Biopotential ampliiers
Second-order Sallen-Key highpass ilter Vi C nc - m + Vo H j j Q where mnc and Q mn n Biopotential ampliiers
Biopotential ampliiers Second-order ilters 3 Band-pass response n =, n =ω Q, n = s Q s s Q s H Q j Q j j H 4 Band-reject response n =, n =, n =ω s Q s s s H Q j j H
Second-order band-reject ilters S. Franco, Design with Operational Ampliiers and Analog Integrated Circuits, Second Edition, 998. Biopotential ampliiers 3
Biopotential ampliiers 4 Twin-T notch ilter - + + - Vo Vi C C C Q j j H 4, Q and C where
Twin-T notch ilter Biopotential ampliiers 5
Twin-T notch ilter Cont. From WJ. Tompkins, JG. Webster. Design o Microcomputer-Based Medical Instrumentation, Prentice-Hall, 98. Biopotential ampliiers 6
Dipole ield o heart when is maximum Biopotential ampliiers 7
Electrocardiogram ECG measurements I II + III = Biopotential ampliiers 8
Augmented Leads Biopotential ampliiers 9
Augmented Leads Biopotential ampliiers 3
elation o dierent-lead ECG Einthoven triangle From WJ Tompkins, Biomedical Digital Signal Processing, Prentice-Hall, 993. Biopotential ampliiers 3
elation o dierent-lead ECG Cont. From WJ Tompkins, Biomedical Digital Signal Processing, Prentice-Hall, 993. Biopotential ampliiers 3
Wilson s central terminal Biopotential ampliiers 33
Chest leads Biopotential ampliiers 34
ECG measurement using chest leads From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998. Biopotential ampliiers 35
ECG at chest leads Biopotential ampliiers 36
-Lead ECG Precordial leads: V -V 6 Einthoven leads: I, II & III Goldberger augmented leads: V, V L & V F Biopotential ampliiers 37
Vectorcardiogram VCG Biopotential ampliiers 38
ECG ampliier + C 4, MΩ, kω 3, 4.5kΩ, 4.5kΩ g, 8.5kΩ AD6 G=7.3 Hz Highpass Filter G =43 - + - Analog Device Application eerence Instrumentation ampliier Drievn-right-leg circuit 49.4k Gain educe common-mode voltage g limits the current to patient. C maintains stability o the circuit. Biopotential ampliiers 39
Intererences in ECG Power-line intererence Electromyographic intererence Biopotential ampliiers 4
Power intererence in ECG measurement Power line, V, 56 Hz C b i b C C C 3 i d3 Zs i d - SShielding Zs i d g Instrumental Ampliier Zcm Driven-right leg circuit + Biopotential ampliiers 4
Common-mode voltage by power-line intererence v i cm db Z G Typical value v cm =. μa 5 kω = mv Biopotential ampliiers 4
Impedance mismatch in ECG measurement Degradation o CM due to nonzero source resistance and parasitic capacitance s C V g - I A Vo Vcm - + s C V + V V due to s C s C Biopotential ampliiers 43
Driven-right-leg circuit V cm V cm s s + - ' cm V cm g a ' a - + + - Biopotential ampliiers 44
Driven-right-leg circuit cont. Vcm id cm Vcm + - a Vo + - Vcm V a V a o V V o cm cm a V cm V cm i d id cm cm a Biopotential ampliiers 45
Driven-right-leg circuit cont. <EX> i d =. μa. A worst-case electrode resistance cm = kω, a and are selected as 5 kω and 5 MΩ respectively. Find V cm. V cm k.a 5M 5k 5V I no right-leg-driven circuit Vcm id cm k.a mv Biopotential ampliiers 46
ECG Ampliier: One-Lead ECG Front-End From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998. Biopotential ampliiers 47
Six-Leads ECG Front-End Five Patient Electrodes Voltage at WCT is equal to dc and 6 Hz common-mode voltage L Drive: Inversion o common-mode intererence From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998.
Magnetic-ield pickup in ECG measurement Biopotential ampliiers 49
Isolation ampliier Basic architecture Equivalent 8 ~ Ω Input Ampliier Modulator Demodulator Output Ampliier Isolation barrier, can be magnetic transormer, optical, capacitive Biopotential ampliiers 5
Isolation ampliier cont. Isolation mode rejection ratio IM V IN Input Common - + V OUT Output Common V IM V OUT V IN where IM VIM Gain IM log IM V IN Gain VIM IM Gain Biopotential ampliiers 5
Isolation ampliier cont. IM v.s. Frequency IM o ISO, Burr-Brown Corporation Biopotential ampliiers 5
Isolation ampliier vs. instrument ampliier Biopotential ampliiers 53
IM vs. CM V OUT V IN VCM CM VIM Gain IM IM ISO >> CM IA > CM ISO ISO: Isolation ampliier IA: Instrumental ampliier Biopotential ampliiers 54
Transormer-coupled isolation ampliier Biopotential ampliiers 55
Transormer-coupled isolation ampliier ISO, Burr-Brown Corporation Biopotential ampliiers 56
Optical-coupled isolation ampliier Biopotential ampliiers 57
Optical-coupled isolation ampliier ISO, Burr-Brown Corporation Biopotential ampliiers 58
Capacitive isolation ampliier ISO, Burr-Brown Corporation Biopotential ampliiers 59
Analog channel-to-channel isolation From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998. Biopotential ampliiers 6
Analog isolation From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998. Biopotential ampliiers 6
Digital isolation From JJ Carr, Introduction to Biomedical Equipment Technology, Prentice-Hall, 998. Biopotential ampliiers 6
Digitization trend in physiological monitoring Biopotential ampliiers 63
Multichannel EEG recodeings: Neuroscan TM Biopotential ampliiers 64
Monopolar measurements Biopotential ampliiers 65
Bipolar measuremesnts Biopotential ampliiers 66
Pasteless biopotential electrodes Monitoring o pilots alertness Detection o gravitationally induced loss o consciousness caused by extreme g-orces during sharp high-speed light Brain state by EEG Muscle atigue and eye blinks and eyeball movement by EMG Skin preparation to decrease skin-electrode impedance is unacceptable or routine prelight procedures Biopotential ampliiers 67
Capacitive active electrode array to record rontal EEG signals Dry electrode Biopotential ampliiers 68
eerence JG. Webster, Medical Instrumentation, application and design, 3rd, Houghton Milin,. JJ.Carr, JM.Brown, Introduction to Biomedical Equipment Technology, 4nd Edition, Prentice-Hall,. S. Franco, Design with Operational Ampliiers and Analog Integrated Circuits, Second Edition, 998. D. Prutchi and M. Norris, Design and Development o Medical Electronic Instrumentation: A Practical Perspective o the Design, Construction, and Test o Medical Devices, John Wiley & Sons, 4. 生物醫學工程導論, 滄海書局,8. Biopotential ampliiers 69