DVNCES in NTURL and PPLIED SCIENCES ISSN: 1995-077 Published YENSI Publication EISSN: 1998-1090 http://www.aensiweb.com/ns 017 June 11(8): pages 366-371 Open ccess Journal Design of Emi Immune io Potential mplifier for EOG 1. suvaran and Dr. G. Elatharasan 1 Teaching fellow, Department of ECE University CollegeOf Engineering, Pattukkottai. ssistant professor, Department of Mechanical Engineering University College Engineering, Pattukkottai. Received 8 February 017; ccepted May 017; vailable online 6 June 017 ddress For Correspondence: Dr. G. Elatharasan, ssistant professor, Department of Mechanical Engineering University College Engineering, Pattukkottai E-mail :gelatharasan@gmail.com; Mobile: 91-944480016 Copyright 017 by authors and merican-eurasian Network for ScientificInformation (ENSI Publication). This work is licensed under the Creative Commons ttribution International License (CC Y). http://creativecommons.org/licenses/by/4.0/ STRCT The Cornea-Retinal Potential (CRP) is the main source of the Electrooculogram (EOG) signals.the human retina consists of an electrically-charged nerve membrane. These potential are in small microvolt and required to be amplified up to the applicable and usable level. The place of electrode attachment, the eyeball rotation, the motion of head, the ambient light as well as the conductivity of skin can also vary this signal. These numerous artifacts with power-line interference, Electro Magnetic interference and other unwanted noise had made the EOG signal quite unattractive for any real biomedical applications. The folded cascodecmos instrumentation amplifier input stage which has an increased immunity to (EMI). The proposed structure uses a source buffered concept with a replica circuit to achieve a higher EMI immunity over a wide range of frequencies, from 10 MHz to 1 GHz. Circuit simulations illustrate how the proposed folded cascode amplifier reduces susceptibility to EMI even in the presence of large amplitude interferences. In the existing system the output is in range of mille volts with noise due to input offset voltage 700mv.In this proposed system the 700mv input offset voltage is given with the input and can get the output is in the range of volts without noise. KEYWORDS: EOG, CRP,increased EMI immunity, folded cascode amplifier, artifacts, electrode potential, Driven right leg, Corneal-Retinal, power line interference. INTRODUCTION EOG is a technique is used to measure the potential difference between the cornea and retina of the eye. The term corneal-retinal potential refers to an electrical difference ( potential ) existing between the cornea and retina of the eye. Retina is the innermost membrane of the eye (ack portion) and cornea is front surface of the eye. The EOG does not measure response to individual visual stimuli. To measure the eye movement, pairs of electrodes are placed both above and below of the eye or the left and right of the eye. If the eye moves from centre position toward one of the two electrodes, this electrode sees the positive side of the retina and the opposite electrode sees the negative side of the retina. Consequently a potential difference occurs between the electrodes. Electric potentials are generated as a result of movement of the eyeballs within the conductive environment of the skull. The generation of EOG signals can be understood by envisaging dipoles (indicating separated positive and negative potential sources) located in the eyeballs. Electrodes placed on either side of the eyes or above and below them pick up the potentials generated by the motion of the eyeball. This potential varies approximately in proportion to the movement of the eyeballs, and hence EOG is sometimes used to study eye positions or disorders of eye movement and balance (a reflex called vestibule-ocular reflex affects the nystagmus of the eye). ToCite Thisrticle:. suvaran and Dr. G. Elatharasan., Design of Emi Immune io Potential mplifier for EOG. dvances in Natural and pplied Sciences. 11(8); Pages: 366-371
367. suvaran and Dr. G. Elatharasan., 017/dvances in Natural and pplied Sciences. 11(8) June 017, Pages: 366-371 1.1 Types of movement of eye: The EOG provides an advantage over other measurements of eye movement because head and body movements do not hinder recording. It is well known that the rectus muscles and the oblique muscles control the movement of the eye. Typical applications of the EOG include the measure the various eye movements. The eye movement can be broadly divided into five categories: blink, saccades, smooth pursuit movements, vengeance movements, and vestibule-ocular movements. The lubrication of the cornea and periodic blanking off of visual information is done by blinking eye movement. Saccades are the short, quick movements during the normal reading, gazing and voluntary Rapid Eye Movement (REM) stage of dreaming and sleeping. The other voluntary and much slower eye movements which are associated with the tracking of an object are Smoothpursuit movements. The movements based on the dilation of pupil, focusing of eye lens, retraction and contraction of the eye ball according to the distance of the particular object are the Vengeance movements. Fig. 1: Electrooculography:Changes in electric field due to eye movement.(a) centered, (b) movement from center towards negative electrode, (c) movement from center towards positive electrode Generation of eog: The eye usually generates a electric potential field which are quite steady and has no relation to any external or internal light stimulation. The presence of this bio potential field can be sensed even when both the eyes are closed or in complete darkness. fixed dipole with positive pole at the cornea and negative pole at the retina can be the practical model of this steady field. Thus it is found that with respect to the retina, the eye generally generate a voltage in the range of 0.40 to 1.0 mv. This is due to the higher metabolic rate at the retina compared to the cornea. This Cornea Retinal Potential (CRP), is usually aligned with the optical axis and (as a result) makes rotation with the direction of our gazing. Fig. : EOG signal generated by horizontal movement of the eye This potential can be measured by electrodes placed on the surface of skin around the eyes. The 5-00 microvolts actual recorded EOG eye potential requires further amplification for processing. With the help of accurate calibration and checking the orientation of the electric dipole, the eyeball angular position with best accuracy which lies within 0 vertically and 1.5 0 horizontally can be tracked. The Cornea-Retinal Potential
368. suvaran and Dr. G. Elatharasan., 017/dvances in Natural and pplied Sciences. 11(8) June 017, Pages: 366-371 (CRP)and eye rotation form the basis of EOG signal and can be measured at the electrode placed around the pair of per orbital surface. III.Implementation:. asic block diagram: asic locks are essential for any EOG circuit shows that the main supply is given to the instrumentation amplifier with driven right leg for pulse generation. It is used for reducing EMI, artifacts and power line interference is provided to the EOG circuit. Fig. 3: lock diagram of EOG amplifier circuit.schematic diagram for eog amplifier circuit: Fig. 4: Schematic diagram of EOG amplifier circuit. Folded cascade amplifier using instead of instrumentation amplifier. The common mode feedback circuit comprises a nmos input stage differential amplifier and a pmos input stage amplifier which are connected in parallel, and a push-pull CMOS amplifier for converting current outputs from the nmos and the input stage differential amplifiers to an output voltage signal. The adoptive bias circuit comprises an operational Tran s conductance amplifier, two current subtraction circuits and four output transistors. The replica folded cascode amplifier gives a low output offset voltage (lesser than 8 mv) up to 300 MHz, and the source-buffered folded cascode amplifier shows a low output offset voltage beyond 300 MHz s. Supply voltages are using instead of electrodes. During filtering decoupling capacitor is used. It is used to reduce EMI, power line interference and artifacts. It is used to overcome the drawbacks in the existing system and it also used. Therefore the high EMI immunity is maintained. C.Driven right leg: This amplification process is accomplished using bio-amplifiers such as operational amplifiers basically instrumentation amplifier. Instrumentation amplifiers serve as an important signal conditioning block at the front end for the amplification of bio signals. In-amps have very high common mode rejection ratio (CMRR) making it useful for amplification. The CMRR ranges between 70 to 100d and can be varied according to the usage of the amplifier. Instrumentation amplifier possesses unique properties like Low dc offset, high CMRR, High gain and compact size, also providing accuracy and stability required for the amplification process.
VDD 3.3V Q19 C 1µF Q18 Q15 10kΩ C4 5pF Q1 Q14 Q16 Q10 C1 1µF R 10kΩ Q17 Q13 Q11 C5 5pF VDD 3.3V Q9 VSS VSS 700mV 700mV Q Q6 Q5 Q7 VDD 3.3V Q8 Q3 Q4 Q1 C3 5pF 369. suvaran and Dr. G. Elatharasan., 017/dvances in Natural and pplied Sciences. 11(8) June 017, Pages: 366-371 Fig. 5: circuit diagram of Driven right leg We used D60N as a front end amplifier. They are very cheap and can be a good precision instrumentation amplifier. The D60 is a very effective preamplifier because of its low input voltage noise of 9 NV/ Hz at 1 khz, 0.8 vs. p-p in the 0.1 Hz to 10 Hz band, and 0.1 P/ Hz input current noises. It can handle weak signals such as bio potential and has high CMRR of 100d. D. Folded cascode amplifier: The common mode comprises a nmos input stage differential amplifier and a pmos input stage amplifier which are connected in parallel, and a push-pull CMOS amplifier for converting current outputs from the nmos and the input stage differential amplifiers to an output voltage signal. The proposed folded cascode amplifier uses transistor dimensions that are identical to the folded cascode amplifier, in order to make a fair comparison. The cut-off frequency of the R-C low-pass filter is chosen to be same as 800 khz. Fig. 6: circuit diagram of folded cascade op amp The cut-off frequency of the R-C low-pass filter is chosen to be same as 800 khz. E.Notch filter: - 4 U6 3 7kΩ 7kΩ C7 0.µF 1 3 8 LM358D C6 4 13kΩ C5 0.1µF 0.1µF Fig. 7: Circuit diagram of Notch filter Multi-Notch Filters are for applications that require the rejection of multiple narrow bands without the use of a multi-filter setup. The Filter passes all frequencies except for the range of 49 to 51Hz.Major problems in bio-potential signals is power line losses and interference.it ranges from 50 to 60 Hz. Notch Filters are used to overcome these losses. It has high frequency compensated and independent.op mp design to operate single supply (3 to 3V) over wide range of supply.
3 7 4 1 5 6 370. suvaran and Dr. G. Elatharasan., 017/dvances in Natural and pplied Sciences. 11(8) June 017, Pages: 366-371 F. High pass filter: High Pass Filter is usually modelled as a linear time-invariant system. It is sometimes called a low-cut filter or bass-cut filter. It s has many uses, such as blocking DC from circuitry sensitive to non-zero average voltages or radio frequency devices. They can also be used in conjunction with a low-pass filter to produce a band pass filter. C1 3 7 1 5 U5 1µF 6 1MΩ 4 - LM741CH Fig. 8: circuit diagram of high pass filter LM741 is overload protection on the input and output and no latch up when the common mode range is exceeded. However, it should freely allow passing the lower end of the frequency band of interest at the same time. It is well known that the EOG signal critical information lies mostly in the frequency range starting from 1 up to 5 Hz. G.Gain amplifier: 7 1 8 560Ω U4 3 6 4-5 U D60N Fig. 9: circuit diagram of Gain amplifier. TLE46CD The D60 is actually based on connection of classic three op amp approach.it is a monolithic IC that also allow the user to program gain with high accuracy with only one single resistor. This versatile D60 is used; the value of resister RG is kept at 560Ω so that the output will be amplified by 100 times. The output can be seen well in the DSO. The EOG signal which is in the microvolt range is amplified to millivolt range. Where, RGis the resistor connected between pin1 and pin8 of the instrumentation amplifier. The opamp gave the gain of 89 (approx. 100) with RG = 560. The IC TLE46CD is only used for more precision ground reference for this highly sensitive amplification. H.Low pass filter. C 4.7µF R U1 C1 3.3µF R4 - LM741CH R3 Fig. 10: circuit diagram of low pass filter. The output of the gain amplifier was given to a Salon-Key Pole utterworth Low Pass Filter with a cutoff frequency of 40Hz. Power line noise can be reduced significantly by this low pass filter with a cut-off frequency of 40Hz. RESULT ND DISCUSSION The considered Opmp circuits were connected in unity gain configuration whereby the EMI signal is injected in the noninverting input terminal.psr in this case is defined as the ratio of small signal output to small signal noise on the supply rail. The above bio-signal amplifier design has two major parts, both the stages give a significant contribution to the total gain.the folded cascode operational amplifier gives high gain so that EMI will reduce. Here the input offset voltage of 700 millivolt is given as input in order to reduce the noise.
371. suvaran and Dr. G. Elatharasan., 017/dvances in Natural and pplied Sciences. 11(8) June 017, Pages: 366-371 Fig. 11: Output Waveform In this proposed system the 700mv input offset voltage is given with the input and can get the output is in the range of volts without noise. During filtering decoupling capacitor is used. It is used to reduce EMI, power line interference and artifacts. It is used to overcome the drawbacks in the existing system and it also used. Therefore the high EMI immunity of dc voltage of EOG circuit is maintained. Conclusion: In this designed circuit the opamp based on instrumentation amplifier is replaced by folded cascodeopamp. novel CMOS folded cascode amplifier is very immune to effects of input offset voltage, which is generated by EMI at PC board. The main advantage of this circuit is increasing EMI immunity and strengthened EOG signal due to easily find out the eye disease. This EOG amplifier is used for many surgical applications such as ophthalmological diagnosis, recording eye movement, cataract, glaucoma etc. here the EOG amplifier circuit is designed and simulated by using multisim software. REFERENCES 1. Qing Jim, Harry Wechsler, ndrew Duchowski and Myron Flicker, 005. Special issue: eye detection and tracking, ComputerVision and Image Understanding, 98(1): 1-3.. Shinier Kawagoe and NobujiTetsutani, 004. Detection and tracking of eyes for gaze-camera control, Image and Vision Computing, (1): 1031-1038. H. Poor, an Introduction to Signal Detection and Estimation. New York: Springer-Verilog, 1985, Ch. 4. 3. Juno Kim, 004. simple pupil-independent method for recording eye movements in rodents using video, Journal of Neuroscience Methods, 138(1-): 165-171. 4. Carlos, H., Morimoto, Marico R.M. Mimic, 005. Eye gaze tracking techniques for interactive applications, Computer Vision and Image Understanding, 98. 5. Malik, Q.. and J. hmad, 007. Retina ased Mouse Control (RMC),World cademy of Science, Engineering and Technology, 7: 318-31. 6. ernard, D., Shaves. 1993. The design and improvement of an eye controlled interface, unpublished. 7. Walgreens, C., S. Van Winkle, J.M. Reroute and M. Stewart, 007. Efficient reduction of electromagnetic interference effects in operational appliers, Electron. Letts, 43(): 84-85. 8. Richelieu,., G. Mating-a, J-M. Reroute, 015. Design of a folded cascodeopamp with increased immunity to conducted electromagnetic interference in 0.18m CMOS, accepted for publication in Microelectronics Reliability.