Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

33 NITTTR, Chandigarh EDIT-2015

High Gain, Low Noise InstrumentationAmplifier Using Three Operational Amplifiers

for Weak Biomedical Signal1Amit Kumar Chidar, 2Pramod Kumar Jain, 3D.S Ajnar

1,2,3Microelectronics and VLSI Design, E&I Department, S.G.S.I.T.S Indore, M.P, India1amitchidar08@gmail.com, 2prjain@sgsits.ac.in, 3ajnards@gmail.com

Abstract:- This paper investigate the performance ofInstrumentation amplifier (INA) using three operationalAmplifier. The proposed circuit works for low input voltageequalised to the heart beat of the human being to analyses theECG (Biomedical application) response. The analyses ofGain, Bandwidth, Unity GBW, Phase margin and outputnoise for operational amplifier used in INA and For the INAGain, Bandwidth, output noise and power Dissipation areanalysed. The proposed circuit designed on UMC 180nmCMOS technology file and all the simulation done onCADENCE SPECTRE Simulator.

Keyword: Amplifier basics, Differential Amplifier usingMOSFET, Operational Amplifier, Instrumentation Amplifier,ECG (Biomedical application), Analog Electronics.

I. INTRODUCTIONToday Biomedical Application play a vital role in the fieldof Technology but, it is very challenging task to fetch thebiomedical signal because of very small amplitude andfrequency of few hertz. As the biomedical signal is verysmall and equal to noise if it is difficult task to find it’spresence. Like Heart Beat signal or Pulse Signal which arevery weak in nature [1, 2]. So, to overcome from thisproblem we need proper amplification, modified Gain,Higher Bandwidth and suppressed noise device like,Instrumentation Amplifier. An instrumentation amplifier isthe one of the most effective block of Biomedical fieldmainly used in some application such as ECG, Transduceror sensor based biomedical devices, MicroelectronicsDevices etc. It provides better amplification, goodlinearity, Gain, Bandwidth and having properties ofsuppressing noise from the weak biomedical signal.Basically it constitute of two differential input and singleended output. The basic building block of biomedicaldevice is shown below in the Fig.1

Fig. 1 Biomedical Signal Fetching and Detecting Device

The Amplifier used in the device shown above is anInstrumentation Amplifier working over the Biomedicalsignal, the Amplifier shows good CMRR, Gain, BW, Lowpower dissipation [3] and Low noise. The Device shownabove with Instrumentation Amplifier provided digital

output pulse after analysing Bio-medical signal. TheBiomedical device such as ECG having quite similarblocks shown in the Fig. 1 and Instrumentation Amplifierplay an important role in it.In this paper, SECTION II and SECTION III describe theoperational amplifier and the proposed instrumentationamplifier respectively. SECTION IV and SECTION Vdescribe the simulation results and conclusion respectively.

II. DESCRIPTION OF OPERATIONAL AMPLIFIERFOR DESIGNING OF INA

The basic building block of proposed circuit is anOperational amplifier. There are three operationalamplifiers used in the proposed INA. Each operationalamplifier is dual stage amplifier basically used to enhancethe gain of the INA. The schematic of operational amplifiershown below in the Fig. 2.

Fig.2 Operational Amplifier for the Proposed INAThe operational amplifier consist [5] of two stages firststage is gain stage and second stage is called output stage.Basically, second stage enhances the gain and providesfrequency compensation through compensationcapacitance Cc. The nmos MOS transistor M1, M2 act asthe differential stage, pmos transistor M3,M4 act as currentmirror, M5, M6 and M8 are used for biasing. The output istaken out from the output load capacitance, the relationshipbetween load capacitance CL and compensationcapacitance CC are shown below:-

CL ≥ 2.2Cc........................(1)Aspect ratio i.e. (W/L ratio) of MOS transistor for theoperational amplifier shown below in the TABLE I:-

TABLE IAspectratio

M1,M2

M3,M4

M5,M6

M7 M8

W/L(µm/ µm)

3/.5 7/.5 12/1 87/.5 75/1

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

33 NITTTR, Chandigarh EDIT-2015

High Gain, Low Noise InstrumentationAmplifier Using Three Operational Amplifiers

for Weak Biomedical Signal1Amit Kumar Chidar, 2Pramod Kumar Jain, 3D.S Ajnar

1,2,3Microelectronics and VLSI Design, E&I Department, S.G.S.I.T.S Indore, M.P, India1amitchidar08@gmail.com, 2prjain@sgsits.ac.in, 3ajnards@gmail.com

Abstract:- This paper investigate the performance ofInstrumentation amplifier (INA) using three operationalAmplifier. The proposed circuit works for low input voltageequalised to the heart beat of the human being to analyses theECG (Biomedical application) response. The analyses ofGain, Bandwidth, Unity GBW, Phase margin and outputnoise for operational amplifier used in INA and For the INAGain, Bandwidth, output noise and power Dissipation areanalysed. The proposed circuit designed on UMC 180nmCMOS technology file and all the simulation done onCADENCE SPECTRE Simulator.

Keyword: Amplifier basics, Differential Amplifier usingMOSFET, Operational Amplifier, Instrumentation Amplifier,ECG (Biomedical application), Analog Electronics.

I. INTRODUCTIONToday Biomedical Application play a vital role in the fieldof Technology but, it is very challenging task to fetch thebiomedical signal because of very small amplitude andfrequency of few hertz. As the biomedical signal is verysmall and equal to noise if it is difficult task to find it’spresence. Like Heart Beat signal or Pulse Signal which arevery weak in nature [1, 2]. So, to overcome from thisproblem we need proper amplification, modified Gain,Higher Bandwidth and suppressed noise device like,Instrumentation Amplifier. An instrumentation amplifier isthe one of the most effective block of Biomedical fieldmainly used in some application such as ECG, Transduceror sensor based biomedical devices, MicroelectronicsDevices etc. It provides better amplification, goodlinearity, Gain, Bandwidth and having properties ofsuppressing noise from the weak biomedical signal.Basically it constitute of two differential input and singleended output. The basic building block of biomedicaldevice is shown below in the Fig.1

Fig. 1 Biomedical Signal Fetching and Detecting Device

The Amplifier used in the device shown above is anInstrumentation Amplifier working over the Biomedicalsignal, the Amplifier shows good CMRR, Gain, BW, Lowpower dissipation [3] and Low noise. The Device shownabove with Instrumentation Amplifier provided digital

output pulse after analysing Bio-medical signal. TheBiomedical device such as ECG having quite similarblocks shown in the Fig. 1 and Instrumentation Amplifierplay an important role in it.In this paper, SECTION II and SECTION III describe theoperational amplifier and the proposed instrumentationamplifier respectively. SECTION IV and SECTION Vdescribe the simulation results and conclusion respectively.

II. DESCRIPTION OF OPERATIONAL AMPLIFIERFOR DESIGNING OF INA

The basic building block of proposed circuit is anOperational amplifier. There are three operationalamplifiers used in the proposed INA. Each operationalamplifier is dual stage amplifier basically used to enhancethe gain of the INA. The schematic of operational amplifiershown below in the Fig. 2.

Fig.2 Operational Amplifier for the Proposed INAThe operational amplifier consist [5] of two stages firststage is gain stage and second stage is called output stage.Basically, second stage enhances the gain and providesfrequency compensation through compensationcapacitance Cc. The nmos MOS transistor M1, M2 act asthe differential stage, pmos transistor M3,M4 act as currentmirror, M5, M6 and M8 are used for biasing. The output istaken out from the output load capacitance, the relationshipbetween load capacitance CL and compensationcapacitance CC are shown below:-

CL ≥ 2.2Cc........................(1)Aspect ratio i.e. (W/L ratio) of MOS transistor for theoperational amplifier shown below in the TABLE I:-

TABLE IAspectratio

M1,M2

M3,M4

M5,M6

M7 M8

W/L(µm/ µm)

3/.5 7/.5 12/1 87/.5 75/1

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

33 NITTTR, Chandigarh EDIT-2015

High Gain, Low Noise InstrumentationAmplifier Using Three Operational Amplifiers

for Weak Biomedical Signal1Amit Kumar Chidar, 2Pramod Kumar Jain, 3D.S Ajnar

1,2,3Microelectronics and VLSI Design, E&I Department, S.G.S.I.T.S Indore, M.P, India1amitchidar08@gmail.com, 2prjain@sgsits.ac.in, 3ajnards@gmail.com

Abstract:- This paper investigate the performance ofInstrumentation amplifier (INA) using three operationalAmplifier. The proposed circuit works for low input voltageequalised to the heart beat of the human being to analyses theECG (Biomedical application) response. The analyses ofGain, Bandwidth, Unity GBW, Phase margin and outputnoise for operational amplifier used in INA and For the INAGain, Bandwidth, output noise and power Dissipation areanalysed. The proposed circuit designed on UMC 180nmCMOS technology file and all the simulation done onCADENCE SPECTRE Simulator.

Keyword: Amplifier basics, Differential Amplifier usingMOSFET, Operational Amplifier, Instrumentation Amplifier,ECG (Biomedical application), Analog Electronics.

I. INTRODUCTIONToday Biomedical Application play a vital role in the fieldof Technology but, it is very challenging task to fetch thebiomedical signal because of very small amplitude andfrequency of few hertz. As the biomedical signal is verysmall and equal to noise if it is difficult task to find it’spresence. Like Heart Beat signal or Pulse Signal which arevery weak in nature [1, 2]. So, to overcome from thisproblem we need proper amplification, modified Gain,Higher Bandwidth and suppressed noise device like,Instrumentation Amplifier. An instrumentation amplifier isthe one of the most effective block of Biomedical fieldmainly used in some application such as ECG, Transduceror sensor based biomedical devices, MicroelectronicsDevices etc. It provides better amplification, goodlinearity, Gain, Bandwidth and having properties ofsuppressing noise from the weak biomedical signal.Basically it constitute of two differential input and singleended output. The basic building block of biomedicaldevice is shown below in the Fig.1

Fig. 1 Biomedical Signal Fetching and Detecting Device

The Amplifier used in the device shown above is anInstrumentation Amplifier working over the Biomedicalsignal, the Amplifier shows good CMRR, Gain, BW, Lowpower dissipation [3] and Low noise. The Device shownabove with Instrumentation Amplifier provided digital

output pulse after analysing Bio-medical signal. TheBiomedical device such as ECG having quite similarblocks shown in the Fig. 1 and Instrumentation Amplifierplay an important role in it.In this paper, SECTION II and SECTION III describe theoperational amplifier and the proposed instrumentationamplifier respectively. SECTION IV and SECTION Vdescribe the simulation results and conclusion respectively.

II. DESCRIPTION OF OPERATIONAL AMPLIFIERFOR DESIGNING OF INA

The basic building block of proposed circuit is anOperational amplifier. There are three operationalamplifiers used in the proposed INA. Each operationalamplifier is dual stage amplifier basically used to enhancethe gain of the INA. The schematic of operational amplifiershown below in the Fig. 2.

Fig.2 Operational Amplifier for the Proposed INAThe operational amplifier consist [5] of two stages firststage is gain stage and second stage is called output stage.Basically, second stage enhances the gain and providesfrequency compensation through compensationcapacitance Cc. The nmos MOS transistor M1, M2 act asthe differential stage, pmos transistor M3,M4 act as currentmirror, M5, M6 and M8 are used for biasing. The output istaken out from the output load capacitance, the relationshipbetween load capacitance CL and compensationcapacitance CC are shown below:-

CL ≥ 2.2Cc........................(1)Aspect ratio i.e. (W/L ratio) of MOS transistor for theoperational amplifier shown below in the TABLE I:-

TABLE IAspectratio

M1,M2

M3,M4

M5,M6

M7 M8

W/L(µm/ µm)

3/.5 7/.5 12/1 87/.5 75/1

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

NITTTR, Chandigarh EDIT -2015 34

III. PROPOSED INSTRUMENTATION AMPLIFIERThe proposed Instrumentation Amplifier consist of threeoperational amplifier and six resistor to carry outmaximum gain [6]. The schematic of proposed circuitshown below in the Fig.3

Fig. 3 Proposed Instrumentation Amplifier (INA)The proposed circuit are basically used to amplifying smallor weak signals of few volts i.e. (0.5mv-4mv) range atsome common mode voltage range [4]. The output anddifferential input voltage relationship for INA are shownbelow:-= −( − ) ∗ ((1 + 2 ) ).............(2)

The resistances of the proposed circuit can be designedthrough the nmos transistor by which the chip area can bereduced.

IV. SIMULATION RESULTSThe proposed circuit is designed on UMC 180nm CMOStechnology file using cadence tool. All the simulatedresults related to Operational Amplifier and Proposed INAis obtained by SPECTRE SIMULATOR tool. Thesimulated results for Operational Amplifier are shownbelow from Fig. 4 to Fig. 6.

Fig. 4 Operational Amplifier Gain

Fig.5 3-dB Bandwidth of Operational Amplifier

Fig.6 Phase Margin and Unity GBW

The related results for Operational Amplifier are shown inthe TABLE II.

TABLE IIResults for Operational Amplifier

PARAMETERS Result Obtained

Technology 180 nm

Supply voltage 1.8 v

Gain 67.083 dB

3-dB Bandwidth 11.496 KHz

Unity GBW 25.2678 MHz

Phase Margin 63.858 deg

B. Simulated Results for Proposed InstrumentationAmplifier (INA)

All the Simulation results for proposed INA i.e. Gain, 3-dBBandwidth and output referred noise are shown below inthe Fig. 7, Fig. 8 and Fig. 9 respectively. All results areobtained by using SPECTRE SIMULATOR tool.

Fig.7 Gain of proposed INA

Fig.8 3-dB Bandwidth of Proposed INA

Fig.9Output Referred Noise (V/sqrt(Hz))

The related results for INA are shown below in the TABLE III.

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

NITTTR, Chandigarh EDIT -2015 34

III. PROPOSED INSTRUMENTATION AMPLIFIERThe proposed Instrumentation Amplifier consist of threeoperational amplifier and six resistor to carry outmaximum gain [6]. The schematic of proposed circuitshown below in the Fig.3

Fig. 3 Proposed Instrumentation Amplifier (INA)The proposed circuit are basically used to amplifying smallor weak signals of few volts i.e. (0.5mv-4mv) range atsome common mode voltage range [4]. The output anddifferential input voltage relationship for INA are shownbelow:-= −( − ) ∗ ((1 + 2 ) ).............(2)

The resistances of the proposed circuit can be designedthrough the nmos transistor by which the chip area can bereduced.

IV. SIMULATION RESULTSThe proposed circuit is designed on UMC 180nm CMOStechnology file using cadence tool. All the simulatedresults related to Operational Amplifier and Proposed INAis obtained by SPECTRE SIMULATOR tool. Thesimulated results for Operational Amplifier are shownbelow from Fig. 4 to Fig. 6.

Fig. 4 Operational Amplifier Gain

Fig.5 3-dB Bandwidth of Operational Amplifier

Fig.6 Phase Margin and Unity GBW

The related results for Operational Amplifier are shown inthe TABLE II.

TABLE IIResults for Operational Amplifier

PARAMETERS Result Obtained

Technology 180 nm

Supply voltage 1.8 v

Gain 67.083 dB

3-dB Bandwidth 11.496 KHz

Unity GBW 25.2678 MHz

Phase Margin 63.858 deg

B. Simulated Results for Proposed InstrumentationAmplifier (INA)

All the Simulation results for proposed INA i.e. Gain, 3-dBBandwidth and output referred noise are shown below inthe Fig. 7, Fig. 8 and Fig. 9 respectively. All results areobtained by using SPECTRE SIMULATOR tool.

Fig.7 Gain of proposed INA

Fig.8 3-dB Bandwidth of Proposed INA

Fig.9Output Referred Noise (V/sqrt(Hz))

The related results for INA are shown below in the TABLE III.

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

NITTTR, Chandigarh EDIT -2015 34

III. PROPOSED INSTRUMENTATION AMPLIFIERThe proposed Instrumentation Amplifier consist of threeoperational amplifier and six resistor to carry outmaximum gain [6]. The schematic of proposed circuitshown below in the Fig.3

Fig. 3 Proposed Instrumentation Amplifier (INA)The proposed circuit are basically used to amplifying smallor weak signals of few volts i.e. (0.5mv-4mv) range atsome common mode voltage range [4]. The output anddifferential input voltage relationship for INA are shownbelow:-= −( − ) ∗ ((1 + 2 ) ).............(2)

The resistances of the proposed circuit can be designedthrough the nmos transistor by which the chip area can bereduced.

IV. SIMULATION RESULTSThe proposed circuit is designed on UMC 180nm CMOStechnology file using cadence tool. All the simulatedresults related to Operational Amplifier and Proposed INAis obtained by SPECTRE SIMULATOR tool. Thesimulated results for Operational Amplifier are shownbelow from Fig. 4 to Fig. 6.

Fig. 4 Operational Amplifier Gain

Fig.5 3-dB Bandwidth of Operational Amplifier

Fig.6 Phase Margin and Unity GBW

The related results for Operational Amplifier are shown inthe TABLE II.

TABLE IIResults for Operational Amplifier

PARAMETERS Result Obtained

Technology 180 nm

Supply voltage 1.8 v

Gain 67.083 dB

3-dB Bandwidth 11.496 KHz

Unity GBW 25.2678 MHz

Phase Margin 63.858 deg

B. Simulated Results for Proposed InstrumentationAmplifier (INA)

All the Simulation results for proposed INA i.e. Gain, 3-dBBandwidth and output referred noise are shown below inthe Fig. 7, Fig. 8 and Fig. 9 respectively. All results areobtained by using SPECTRE SIMULATOR tool.

Fig.7 Gain of proposed INA

Fig.8 3-dB Bandwidth of Proposed INA

Fig.9Output Referred Noise (V/sqrt(Hz))

The related results for INA are shown below in the TABLE III.

Int. Journal of Electrical & Electronics Engg. Vol. 2, Spl. Issue 1 (2015) e-ISSN: 1694-2310 | p-ISSN: 1694-2426

35 NITTTR, Chandigarh EDIT-2015

TABLE IIIResults for Proposed Instrumentation Amplifier

PARAMETER Thiswork

[4] [6] [7]

Technology (um) 0.18 0.18 0.5 0.8Supply voltage 1.8v N/A N/A N/A

Gain (dB) 42.330 19.6 19.9 40Bandwidth 135.91

KHzN/A N/A N/A

Output noise(V**2/(Hz))

3.05µ N/A N/A N/A

Power dissipation 0.792mW

N/A N/A 122u

V. CONCLUSIONThe proposed Instrumentation Amplifier basically used foramplifying the small amplitude and low frequency signalequalized to heart beat or pulse. The designed circuitshows high gain, low power dissipation and smaller areawise. The supply voltage of 1.8 volts required for thecircuit. All the simulation results are clearly obtained bythe help of cadence spectre simulator.

REFERENCESChien-Jung Chou; Bing-Jye Kuo; Li Guang Chen, Po-Yun Hsiao andTsung-Hsien Lin, “A 1-V low noise readout front end for biomedicalapplications in 0.18μm CMOS,” In Proc. Int. Symp. VLSI-DAT., HsinChu, pp. 295-298, Apr 2010.Yazicioglu,R.F.; Merken,P and Van Hoof, C.,“ Integrated low power 24-channel EEG front end” Electronic Letter, vol. 41 no. 8, pp 457-458,Apr2005.Shojaei-Baghini, M.; Lal, R.K.; and Sharma, D.K., “An ultra low powerinstrumentation amplifier for biomedical application,”Int.Workshop IEEE(B.C.S) Dec 2004, pp 691-699 April 2004.Yasin,F.M.; Yap,M.T.;and Reaz,M.B.I ,“CMOS Instru-mentationAmplifier with Offset Cancellation Circuitry for BiomedicalApplications,” In Proc. of 5th WSEAS, Spain, pp 168-171, 2006.Philip E. Allen and Douglas R.Holberg, CMOS Analog Circuit Design,Oxford University Press, pp 180-196, March 2002.Chih-Jen Yen ; Wen-Yaw Chung and Mely Chen Chi ,“Micro-PowerLow Offset Instrumentation Amplifier IC Design For BioMedical SystemApplications”,IEEE Transactions On Circuits And Systems-I:RegularPapers ,Vol.51,No.4, pp 691-699 April 2004.Ananth, R.S. and Lee, E.K., “Design of a low power implantableelectromyogram amplifier,” In Proc.IEEE Inter.Symp.on Circuits andSystems (ISCAS’04), vol 4, pp. 9-12, 2004.