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Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor

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Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 12-2010 Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor Ankit Master University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Electrical and Electronics Commons, and the VLSI and Circuits, Embedded and Hardware Systems Commons Recommended Citation Master, Ankit, "Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor. " Master's Thesis, University of Tennessee, 2010. https://trace.tennessee.edu/utk_gradthes/820 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Ankit Master entitled "Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Electrical Engineering. Benjamin J. Blalock, Major Professor We have read this thesis and recommend its acceptance: Syed K. Islam, Aly E. Fathy Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a thesis written by Ankit Chandrakant Master entitled “Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor.” I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Electrical Engineering. Benjamin J. Blalock, Major Professor We have read this thesis and recommend its acceptance: Syed K. Islam Aly E. Fathy Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official student records.) Design and Implementation of a Signal Conditioning Operational Amplifier for a Reflective Object Sensor A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Ankit Chandrakant Master December 2010 Thank you Chandra! ii ABSTRACT Industrial systems often require the acquisition of real-world analog signals for several applications. Various physical phenomena such as displacement, pressure, temperature, light intensity, etc. are measured by sensors, which is a type of transducer, and then converted into a corresponding electrical signal. The electrical signal obtained from the sensor, usually a few tens mV in magnitude, is subsequently conditioned by means of amplification, filtering, range matching, isolation etc., so that the signal can be rendered for further processing and data extraction. This thesis presents the design and implementation of a general purpose op amp used to condition a reflective object sensor’s output. The op amp is used in a non-inverting configuration, as a current-to-voltage converter to transform a phototransistor current into a usable voltage. The op amp has been implemented using CMOS architecture and fabricated in a 0.5-µm CMOS process available through MOSIS. The thesis begins with an overview of the various circuits involving op amps used in signal conditioning circuits. Owing to the vast number of applications for sensor signal conditioning circuits, a brief discussion of an industrial sensor circuit is also illustrated. This is followed by the complete design of the op amp and its implementation in the data acquisition circuit. The op amp is then characterized using simulation results. Finally, the test setup and the measurement results are presented. The thesis concludes with an overview of some possible future work on the sensor-op amp data acquisition circuit. iii TABLE OF CONTENTS CHAPTER 1 INTRODUCTION................................................................................................. 1 1.1 Motivation ........................................................................................................ 1 1.2 Scope of the Thesis........................................................................................... 2 1.3 Organization of the Thesis................................................................................ 2 CHAPTER 2 SENSOR SIGNAL CONDITIONING................................................................ 4 2.1 Operational Amplifiers – Fundamentals .......................................................... 4 2.2 Signal Conditioning Applications .................................................................... 5 2.2.1 Semiconductor Temperature Sensors...................................................... 6 2.2.2 High Impedance Charge Output Sensors................................................. 8 2.2.3 Resistive Bridge Sensors ......................................................................... 9 2.3 Industrial Sensor Illustration ...........................................................................11 CHAPTER 3 OP AMP DESIGN............................................................................................... 13 3.1 Op amp Architecture ...................................................................................... 13 3.1.1 Input Stage ............................................................................................ 13 3.1.2 Output Stage........................................................................................... 14 3.1.3 Current Mirror........................................................................................ 14 3.2 Complete Schematic....................................................................................... 16 3.2.1 Open-loop Gain...................................................................................... 16 3.2.2 Frequency Compensation....................................................................... 18 3.2.3 Input common mode range ................................................................... 18 iv 3.2.4 Noise ..................................................................................................... 19 3.2.5 Slew Rate .............................................................................................. 20 3.3 Simulation Results.......................................................................................... 20 3.4 Layout and Implementation............................................................................ 24 CHAPTER 4 OP AMP MEASUREMENT RESULTS .......................................................... 26 4.1 Test Setup ....................................................................................................... 26 4.1.1 Input common mode range.................................................................... 26 4.1.2 Open-loop gain....................................................................................... 27 4.1.3 Small-signal analysis............................................................................. 29 4.1.4 Large-signal analysis (Slew rate)........................................................... 31 4.1.5 Input-referred noise................................................................................ 31 4.1.6 PSRR...................................................................................................... 33 4.1.7 CMRR.................................................................................................... 35 4.2 Summary......................................................................................................... 36 CHAPTER 5 SYSTEM APPLICATION................................................................................. 37 5.1 Width measurement ....................................................................................... 37 5.2 System level circuit setup............................................................................... 37 5.3 System noise floor .......................................................................................... 39 CHAPTER 6 CONCLUSIONS ................................................................................................. 41 6.1 Future Work.................................................................................................... 41 REFERENCES ........................................................................................................................... 42 APPENDIX ................................................................................................................................. 44 v A.1 Calculation of Open-loop Gain ..................................................................... 45 A.2 Test Board ..................................................................................................... 46 VITA ........................................................................................................................................... 47 vi TABLE OF TABLES Table 1.1 - Op amp Specifications.................................................................................................
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