1,720,973 research outputs found
A new process for gated silicon field emitter arrays fabrication
No full textA new process for, gated silicon field emitter arrays fabrication is presented. The fabrication process is based on the photoelectrochemical silicon etching in HF electrolyte solution, a well known technique for macropore array formation. For the first time, we have successfully used this technique to produce very regular silicon microtips array with high aspect ratio (tip height/tip width ratio). The process is able to fabricate field emitter array with self-aligned chromium metal gate using only one mask
Very low flow rate behaviour of micromachined hot-plate anemometers
No full textThe increase of microfluidic applications has led to a growing request for accurate
miniaturized flow sensors, suitable for operating in gas velocity as low as few cm/s. In this work a classic
micromachined anemometer, consisting of a suspended membrane equipped with a polysilicon heater and
a p-poly/n-poly thermopile as the temperature sensor, has been analytically and experimentally
characterized in very low nitrogen flow rates. The sensor operating limits in terms of sensitivity and
dynamical range have been investigated and some solutions to improve the sensor performances are
proposed
A Class AB CMOS Operational Amplifier for Application as Rail-to-Rail High Current Drive Buffer
No full textA class AB CMOS operational amplifier specially designed to be used as unity gain buffer is presented. The novelty of the presented topology consists in using a classical rail-to-rail OTA with duplicated output port to drive the gates of the op-amp complementary output transistors and relying on a separate feedback loop to limit the quiescent current. The simplicity of classical two stage op-amps is maintained with advantages in terms of die size, transient response and process independence. The circuit, fabricated using the BCD3S process of STMicroelectronics, occupies a die size of 0.06 mm2 and operates from a single 2.2V power supply with resistive loads as low as 300 Ω
A high current drive CMOS output stage with a tunabel quiescent current limiting circuit
No full textA CMOS output stage based on a complementary
common source with an original quiescent current limiting circuit
is presented. The quiescent current can be varied over a wide range
by means of a control current with no need to modify the transistor
aspect ratios. The output stage has been coupled to a conventional
complementary input stage to form a rail-to-rail buffer. A prototype
with the inclusion of auxiliary pins for biasing and current
monitoring purposes has been designed using the 1- m doublepolysilicon
BCD3S process of STMicroelectronics. On a single 5-V
power supply, the maximum output current is 20 mA. The amplifier,
biased for a total power dissipation of 1 mW, exhibits a total
harmonic distortion of 58 dB at 1 kHz with 4-V peak-to-peak on
a 330-
load. Correct operation of the quiescent current limiting
circuit has been demonstrated for a minimum supply voltage of
2.2 V
A flow sensor for liquids based on a single temperature sensor operated in pulsed mode
No full textAn anemometric flow sensor for liquids based on a single temperature sensor is presented. The sensor is based on a probe composed by
a silicon chip glued to a copper cylinder acting as thermal feed-through. A precise temperature sensor and a resistive heater are integrated
on the chip surface. The sensor is operated in pulsed mode to eliminate the interference of the fluid temperature, switching either the heater
power or the probe temperature. The results of water flow tests in the range (1–30) l/h are presented. The problem of reducing the duration
of the measurement cycle has been addressed with theoretical and experimental arguments
Single temperature sensor anemometer for liquid flow detection with pulsed heating driver
No full textIn this work we present an integrated
anemometer for liquids based on a single
temperature sensor. By means of a proportional
control loop, which utilises a PWM signal to
maintain the sensor temperature at a constant value,
the measurement time resulted four times faster
than the intrinsic thermal settling time of the sensor
A Closed-Loop Mass Flow Controller Based on Static Solid-State Devices
No full textA mass flow controller, based on an integrated flow
sensor and a thermally actuated solid state regulator, is presented.
The sensor is a miniaturized differential calorimeter obtained by
postprocessing a silicon chip fabricated by a standard microelectronic
process. The regulator consists in a microchannel etched
into the surface of a silicon substrate and sealed with a glass plate,
joined to the silicon die using anodic bonding. Flow regulation
is achieved by varying the channel temperature by means of a
chromium resistor. The two devices are connected in closed-loop
through a low noise—low offset electronic circuit. Experimental
data, demonstrating the effectiveness of the flow controller, are
presented. Limitations of the proposed approach and possible
improvements are discussed
DC feedback technique for temperature stabilisation of tunable CMOS transconductors,
No full textA simple technique for stabilising the transconductance of CMOS
transconductors against temperature variations, with no need of
external frequency reference signals, is presented. Accurate electrical
simulations demonstrated that a 2.6% maximum transconductance
variation over the temperature range 55–150 C and a 600% tuning range can be obtaine
Sensitivity improvement of integrated anemometers obtained by jet flow impingement
No full textA typical integrated hot wire flow sensor, fabricated by means of micromachining, has been characterized in order to evaluate the low
flow detection capabilities. The lowest detectable flow has been related to a sensitivity threshold, due to the forced to free convection
transition. A simple lumped element model have been used to show the dependence of the sensitivity threshold on the sensor dimensions
and the physical parameters of the gas. The resort to the high heat transfer coefficients of fluid jets has been presented as a valid method
to improve the sensitivity of the devices. Measurements of the sensor response for various jet diameters and incidence angles have been
reported and discussed
Flicker noise in heterocyclic conducting polymer thin film resistors
No full textThe power spectral density of low frequency resistance fluctuation in heterocyclic conducting polymer thin film resistors was measured at various temperatures and bias current values. An accurate calculation of the background noise was performed in order to correct the measured power spectral densities. A parameter obtained normalizing the voltage power density to the sample volume and d.c. bias is used to compare the tested conducting polymers with various materials used for resistors fabrication
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