Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

William Wilson
M.S. Final
May 15, 2014, 10:00 a.m.
201 - Scott Bioengineering: Atlas Design Studio
Abstract: Biosensor devices have found an increasingly broad
range of applications including clinical,
biological, and even pharmaceutical research and
testing. These devices are useful for detecting
chemical compounds in solutions and tissues.
Current visual or optical methods include
fluorescence and bio/chemiluminescence based
detection. These methods involve adding
luminescent dyes or fluorescent tags to cells or
tissue samples to track movement in response to a
stimulus. These methods often harm living tissue
and interfere with natural cell movement and
Electrochemical biosensing methods may be
used without adding potentially harmful dyes or
chemicals to living tissues. Electrochemical
sensing may be used, on the condition that the
desired analyte is electrochemically active, and
with the assumption that other compounds present
are not electrochemically active at the reduction
or oxidation potential of the desired analyte. A
wide range of analytes can be selectively detected
by specifically setting the potential of the
solution using a potentiostat. The resulting
small-magnitude current must then be converted to
a measurable voltage and read using a low-noise
transimpedance amplifier.
To provide spatial resolution on the
intra-cellular level, a large number of electrodes
must be used. To measure electrochemical signals
in parallel, each electrode requires a minimum of
a transimpedance amplifier, as well as other
supporting circuitry. Low power consumption is a
requirement for the circuitry to avoid generating
large amounts of heat, and small size is necessary
to limit silicon area.
This thesis proposes the design of a low-
noise, low-power transimpedance amplifier for
application in integrated electrochemical
biosensor devices. The final proposed design
achieves a 5MΩ transimpedance gain with 981aA/√Hz
input inferred noise, 8.06µW at 0.9V power supply,
and occupies a silicon area of 0.0074mm2 in a
commercial 0.18µm CMOS process. This thesis also
explores the development of a multi-channel
electrochemical measurement system.
Adviser: Tom Chen
Co-Adviser: N/A
Non-ECE Member: Chuck Henry
Member 3: Ali Pezeshki
Addional Members: N/A
Wilson, W.; Chen, T.; Selby, R., "A current-starved inverter-based differential amplifier design for ultra-low power applications," Circuits and Systems (LASCAS), 2013 IEEE Fourth Latin American Symposium on , vol., no., pp.1,4, Feb. 27 2013-March 1 2013

Wilson, W.; Chen, T. "Design of a 50MO Transimpedance Amplifier with 0.98fa/vHz Input Inferred Noise in a 0.18uM CMOS Technology" BIODEVICES 2014. March. 3 2014-March 6 2014
Program of Study:
ECE 699