IPASJ International Journal of Electrical Engineering (IIJEE)
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
A design for Epileptic Seizure Prediction to
boost performance issues low power, low noise
neural signal signal amplifier
Md. K. Hussain
M.sc in Electrical engineering, Faculty of Electrical Engineering, K. N. Toosi University of Technology, Iran, Tehran
ABSTRACT
This paper deals with the look of low power low noise neural signal electronic equipment for convulsion Prediction. The advent
of Micro-electro Arrays has driven the requirement for implantable electronic electronic equipment to sight those animate
thing neural signals (ENG). we tend to projected a preamplifier of absolutely differential Low Noise electronic equipment
(LNA) with gramme boosting in order to boost the gain further as cut back the facility consumption. Low frequency high pass
operate has been accomplished with anti-parallel Diode connected PMOS. Simulation results shows that the input referred
noise is one.24μVrms from 100Hz to five KHz, mid-band voltage gain of 44.6dB, and also the power consumption is
eighteen.74μw. a brand new signal process circuit has been designed extract the seizure onset. The results area unit valid
victimization Cadence spectre machine with 180nm technology. Simulation results show that this implantable electronic
equipment is appropriate for convulsion prediction.
Keywords: convulsion, NSA, pseudo resistance, Low frequency High Pass operate (LFHPF)
1. INTRODUCTION
Early prediction of severe encephalopathy could useful for the patients to flee from fatal accidents. Much research is
being done on convulsion prediction using graphical record Signals. Whereas exploitation graphical record signals
several false positives square measure according. So, the higher alternate for this system is to use implantable devices
recording ENG signals. ENG signals square measure tiny in amplitude from 5μV to 500μV and have a coffee frequency
spectrum of 100Hz to five KHz[1]. but in observe, the distance of Micro-electrode arrays (MEA) square measure
difficult to regulate and therefore the ensuing ENG is extremely small requiring a LNA for signal amplification humor
detection.
The overall diagram for convulsion detection is shown in figure1. Output from the ENG signal acquisition electronic
equipment (NSA) is directly taken as clinical knowledge, more the signal is shipped through a proposed
straightforward signal processor to extract the seizure onset. Later the extracted feature are going to be compared with
the reference neural signal Potential (Vsyn) exploitation high speed latch comparator.[2]. The composite Neural signal
consists of huge DC offset due to the humor wherever the MEA resides and Electromyography (EMG) noise, Power
Line frequency interference. The DC offset and myogram noise may be removed by Low frequency High Pass Function
[3].
MOSFET based mostly style for low frequency medical specialty application has inherent flicker noise, it cause poor
SNR. a number of the solutions to scale back the flicker noise square measure chopper stabilization and Autozeroing,
Volume 1, Issue 1, June 2013
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IPASJ International Journal of Electrical Engineering (IIJEE)
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
both cases consumes additional power, it is not advisable for implantable applications [4,5]. The flicker noise is
dominating within the PMOS. The glint noise and therefore the valid signals square measure having identical 150Hz
spectrum, therefore the transistors created massive to increase its transconductance (gm) [6], thereby the noise is
eliminated. The projected LNA with subthreshold PMOS input combine with gm- boosting shows valid results.
Figure1. Overall Block Diagram of Epileptic Seizure Detection
This LNA has absolutely differential topology so as to eliminate the coherent noise. The planning of low frequency
High pass perform is difficult one. In our projected Circuit Anti-parallel Diode connected PMOS is employed as Pseudo
resistance. It consumes less power and exhibits additive characteristics. The differential output is regenerate into single
complete by the high linear OTA-C filter, that is nothing however a Low pass Filter during this design[6].
2. INDUCTIVE COUPLED RAIL-TO-RAIL SUPPLY
Figure 2 Rail-to-Rail Rectifier Circuit
For the past few years, superior implantable bio-medical ICs plays a significant role in modern drugs. With the
appearance of nanotechnology, Battery based mostly circuits don't seem to be entertained for implantable applications.
Nowadays, inductively coupled link is additional fascinating methodology for patient, due to its high power transfer
efficiency and safety. Bio-medical amplifiers shows good result, once exploitation rail-to-rail power provide. In the
projected methodology, the curved output from the secondary coil is applied between the terminals X and Y. once
potential on facet X is over that of Y, the transistors Mb,Mc,Mf and Mg square measure forces to shutoff while Ma,
Md, Me and Mh square measure turned on.
Therefore, we will get completely and negatively unidirected provide from terminals +Vr and –Vr respectively for each
positive and negative 0.5 cycles. The unidirected provide is tried and true a capacitor filter to get rid of its ac contents
(ripples). By using a appropriate regulator we will a dc for the circuit. For the regulation, zener diode isn't most
popular because of its parasitic capacitance.
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IPASJ International Journal of Electrical Engineering (IIJEE)
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
3. PSEUDO-RESISTORS
The Pseudo-resistors plays an important role within the realization of low frequency high pass perform, in order to
avoid massive on-chip capacitance ensuing high power consumption and poor SNR, The resistors of the order of many
Giga- ohms square measure required for this circuit[7]. There square measure six totally different structures as shown
in the figure3.The linear variation of current for every structure is premeditated for comparison.
Figure 3. Totally different Structures of Pseudo-Resistor
The transfer characteristics for single and anti-parallel connected is shown within the figure4. From this I-V curve we
will perceive the anti-parallel connected (DoubDio & DoubSG) pseudo resistance exhibits bilinear characteristics.
The figure3.(e,f) uses subthreshold PMOS and deep-depletion NMOS respectively. In each cases, it desires extra
biasing for calibration purpose. For implantable applications, the supply is applied outwardly through inductive
coupling. so the planning with sizable amount of biasing isn't most popular. Figure3. (c,d) shows additive
characteristics and doesn’t need extra biasing for calibration purpose. Out of those 2, Figure3.c is better fitted to this
application as a result of high dimensionality.
4. LOW FREQUENCY HIGH PASS FUNCTION
This circuit serves two functions. First, it avoids the DC voltage price of the humor wherever the MEAs square measure
placed, as a result of Dc voltage could saturate the output of LNA. Second, it removes the myogram noise spectrum that
resides among 100Hz. This circuit is constructed by the pseudo-resistors, so as to avoid the high power consumption.
The mid-band gain price is ready by the capacitors C1 and C2[8]. For bio-medical implantable applications, middle
band- gain normally chosen by the magnitude relation of c1 and c2 as fifty. We can use either open loop or control
system configuration as shown in figure.6.
Volume 1, Issue 1, June 2013
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IPASJ International Journal of Electrical Engineering (IIJEE)
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
Figure 6. Open Loop and control system Configuration
Simulation results show that the open loop configuration is healthier as a result of the high gain and Low Power
consumption. No stability drawback arises around the region of interest.
5. LOW NOISE ELECTRONIC EQUIPMENT (LNA)
Figure.7 LNA circuit diagram
Figure7 shows the absolutely differential LNA circuit. Two sub-threshold PMOS input semiconductor unit combine M1
and money supply plays an important role to scale back the glint (1/f) noise within the circuit, as a result of it can't be
eliminated in the succeeding stages[10]. Most of the designers prefer PMOS than NMOS; the rationale behind this can
be NMOS provides additional gain and additional noise. To reduce the flicker noise, we've to decide on the
transconductance gm1 >> gm3 > gm5 by ever-changing W/L ratio. To extend the transconductance of the
input semiconductor unit, we tend to use gm-boosting methodology to steer the current into the changed active load.
The transconductance may be varied by ever-changing the W/L ratio of the M5, M7. The on top of aforesaid condition
Volume 1, Issue 1, June 2013
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IPASJ International Journal of Electrical Engineering (IIJEE)
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
additionally applicable to the negative counterpart of the amplifier. This projected methodology of active load increases
the gain of the electronic equipment with low power consumption. The transistors M20, M21and M22 provide the
biasing to LNA.
6. LOW PASS FILTER
High linear, OTA-C filter based mostly straightforward Low pass filter. Dimensionality of the low pass filter is
improved by supply degeneration topology. During this circuit the transistors biased on triode region. M25-M26 add a
saturation-active mode for positive Vin in associate degree active-saturation mode for negative Vin, may end up in a
very linear operation.
7. DRIVEN SIGNAL PROCESSOR
For implantable bio-medical applications, gate driven MOSFET move threshold voltage constraint. A new processor
exploitation bulk-driven MOSFET has been developed to handle terribly tiny signals within the range of many
millivolts. Both, bulk-driven and gate-driven performances square measure same except the physical size of former is
tiny. the primary order equation shows the VBS and its result on drain current.
The seizure onset from the neural signal may be clipped-off by the processor. Later, it compared with the reference
signal exploitation high speed latch comparator. Thereby, seizure onset may be detected.
Neural signal from the amplifier is applied at the majority of semiconductor unit MA. Here, Gate and supply is tied to
create VGS constant.
Therefore, the output variation is simply as a result of bulk potential. once input is larger than zero, inverse depletion
layer is created and it causes current to flow through the semiconductor unit MA. The neural reference potential VSYN
for the conventional behavior is applied to the bulk of MB.
The Combination of MA& MB blocks all signal whose price is a smaller amount than the reference potential
(VSYN). So the onset feature may be extracted.
8. CONCLUSION
The neural signal acquisition electronic equipment with 18.24μw and 1.24μVrms over the 100Hz – 5kHz has been
bestowed. A new signal process circuit has been developed exploitation two semiconductor unit reduces overall power
consumption. Simulation results shows that this circuit is intended to satisfy all necessities for the detection and
warning to the encephalopathy affected patients for safety and clinical contexts.
REFERENCES
[1.] T.Yoshita, Y.Mausi, T.Mashimo, “ A 1 V Low-Noise CMOS Amplifier Using Autozeroing and Chopper
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[9.] Nazanin Neshatvar, “Design of Low Frequency High Pass Filter using Pseudo resistors”, Bio-medical
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IPASJ International Journal of Electrical Engineering (IIJEE)
A Publisher for Research Motivation........
Volume 1, Issue 1, June 2013
Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
Email: editoriijee@ipasj.org
ISSN 2321-600X
[10.] Muhammad Tariqus Salam, Mohamad Sawan, Anas Hamoui, and Dang Khoa Nguyen, “Low-power CMOSbased
epileptic seizure onset detector”
[11.] Kris Iniewski. “VLSI Circuits for Bio-medical Applications”
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