Tech Briefs Magazine - August 2021 - 23

High-Temperature Silicon Carbide Op Amps Fabrication
Applications include sensor signal conditioning in harsh conditions such as automotive,
oil and gas operations, and firefighting.
John H. Glenn Research Center, Cleveland, Ohio
N
ASA Glenn has developed a method
to correct for variations in transistor
threshold voltage due to die location on
the wafer for silicon carbide (SiC) op
amps, enabling improved electrical circuits
for sensor signal conditioning in
harsh environments. Important systemlevel
benefits are enabled by improved
performance data from sensor circuitry
mounted within very hot gas turbine flows
or the primary coolant loop of a nuclear
reactor, for example.
Often, tiny (microvolt) signals from
sensors require conditioning by hightemperature
electrical components to
filter, amplify, and convert to levels suitable
for digitization and " smart " system
control. Op amps are a critical component
for signal amplification. With the
threshold voltage correction scheme,
the signal amplification of all op amps,
at any position on the SiC wafer, is the
same, extending reliable signal conditioning
well be yond the current temperature
limits of conventional silicon integrated
circuits, allowing useful chips to
be produced across the entire SiC wafer
surface.
For robust operational amplifiers based
on SiC Junction Field Effect Transistors
(JFETs), this compensation method mitigates
issues with threshold voltage variations
that are an effect of die location on
the wafer. Modern high-temperature op
amps on the market fall short due to temperature
limits (only 225 °C for siliconbased
devices).
Previously, researchers noted that multiple
op amps on a single SiC wafer had different
amplification properties due to different
threshold voltages that varied spatially
as much as 18%, depending on the
circuit's distance from the SiC wafer center.
While 18% is acceptable for some applications,
other important system ap plications
demand better precision. By applying this
technology to the amplifier circuit design
process, the op amp will provide the same
signal gain no matter its position on the
wafer. The compensation approach en -
ables practical signal conditioning that
works from 25 °C up to 500 °C.
NASA is actively seeking licensees to commercialize
this technology. Please contact
NASA's Licensing Concierge at AgencyPatent-Licensing@mail.nasa.gov
or call us
at 202-358-7432 to initiate licensing discussions.
Follow this link for more information:
https://technology.nasa.gov/patent/LEWTOPS-160.
Device
Powers Wearable Sensors Through Human Motion
A triboelectric generator made of flexible circuit boards creates electricity when
the wearer moves.
California Institute of Technology, Pasadena, California
T
he advent of inexpensive wearable
sensors that can monitor heart
rate, body temperature, and levels of
blood sugar and metabolic byproducts
has allowed researchers to monitor
human health in ways never
before possible. But like all electronic
devices, these wearable sensors need
a source of power. Batteries are an
option but are not necessarily ideal
because they can be bulky, heavy, and
run out of charge.
Researchers have now developed a
way to power wireless wearable sensors
by harvesting kinetic energy that
is produced by a person as they move
around. This energy harvesting is
done with a thin sandwich of materials
(Teflon, copper, and polyimide)
attached to the person's skin. As the
person moves, these sheets of material
rub against a sliding layer made of
copper and polyimide and generate
small amounts of electricity. The effect,
known as triboelectricity, is perhaps best
illustrated by the static electric shock a
Tech Briefs, August 2021
Cov
the torso and a slider that is attached
to the inside of the arm. The slider
slides against the stator during hu -
man motion and an electrical current
is generated at the same time. The
nanogenerator was made with commercially
available flexible circuit
boards.
The triboelectric generator is made of commonly available
commercial materials and creates electricity when
the wearer moves. (Credit: Caltech)
person might receive after walking
across a carpeted floor and then touching
a metal doorknob.
The triboelectric generator (nanogenerator)
has a stator that is fixed to
www.techbriefs.com
ToC
The nanogenerator does not create
a lot of electricity; one would
need a device with 100 square meters
of surface area to power a 40-watt
light bulb. The wearable sensors have
low power re quirements and the system
stores generated electricity in a
capacitor until there is enough
charge to take a reading from the
sensor and wirelessly send the data to
a cellphone through Bluetooth. The
more a person moves, the more often
the sensor can collect data. Even if
the person is fairly sedentary, however,
the sensor eventually will accumulate
enough power to operate.
For more information, contact Emily Velasco
at evelasco@caltech.edu; 626-372-0067.
23
https://technology.nasa.gov/patent/LEW-TOPS-160 http://www.techbriefs.com http://www.abpi.net/ntbpdfclicks/l.php?202108MDNAV

Tech Briefs Magazine - August 2021

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Tech Briefs Magazine - August 2021 - Intro
Tech Briefs Magazine - August 2021 - Sponsor
Tech Briefs Magazine - August 2021 - Cov1
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