231 research outputs found
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Low-Frequency Medium Power Capacitor-Free Self-Resonant Wireless Power Transfer
Quasi-digital low-dropout voltage regulators uses controlled pass transistors
This article presents a low quiescent current output capacitorless quasi-digital CMOS LDO regulator with controlled pass transistors according to load demands. The pass transistor of the LDO is broken up to two smaller sizes based on a breakup criterion defined here, which considers the maximum output voltage variations to different load current steps to find the suitable current boundary for breaking up. This criterion shows that low load conditions will cause more output variations and settling time if the pass transistor is used in its maximum size. Therefore, using one smaller transistor for low load currents, and another one larger for higher currents, is the best trade-off between output variations, complexity, and power dissipation. The proposed LDO regulator has been designed and post-simulated in HSPICE in a 0.35 µm CMOS process to supply a load current between 0-100 mA while consumes 7.6 µA quiescent current. The results reveal 46% and 69% improvement on the output voltage variations and settling time, respectively.Postprint (published version
Analysis of Passive Charge Balancing for Safe Current-Mode Neural Stimulation
Charge balancing has been often considered as one
of the most critical requirement for neural stimulation circuits.
Over the years several solutions have been proposed to precisely
balance the charge transferred to the tissue during anodic and
cathodic phases. Elaborate dynamic current sources/sinks with
improved matching, and feedback loops have been proposed with
a penalty on circuit complexity, area or power consumption.
Here we review the dominant assumptions in safe stimulation
protocols, and derive mathematical models to determine the
effectiveness of passive charge balancing in a typical application
scenario
Inverter-Based Low-Voltage CCII- Design and Its Filter Application
This paper presents a negative type second-generation current conveyor (CCII-). It is based on an inverter-based low-voltage error amplifier, and a negative current mirror. The CCII- could be operated in a very low supply voltage such as ±0.5V. The proposed CCII- has wide input voltage range (±0.24V), wide output voltage (±0.24V) and wide output current range (±24mA). The proposed CCII- has no on-chip capacitors, so it can be designed with standard CMOS digital processes. Moreover, the architecture of the proposed circuit without cascoded MOSFET transistors is easily designed and suitable for low-voltage operation. The proposed CCII- has been fabricated in TSMC 0.18μm CMOS processes and it occupies 1189.91 x 1178.43μm2 (include PADs). It can also be validated by low voltage CCII filters
Design of a Reference Buffer for a Delta-Sigma ADC with Current DAC
In analog to digital conversion, it’s necessary to provide a reference voltage to the Analog
to Digital Converter (ADC), in order to quantify the input signal. However, as the
ADC has a switch constantly commuting on its input it will cause perturbations on the
reference voltage provided by the Bandgap circuit. Thus, it will interfere with the normal
behaviour of the Bandgap circuit, which will longer be capable of provide the desired
reference voltage.
Besides, if the reference voltage is not constant in the desired value the output code generated
by the ADC will have errors.
In order to avoid conversion errors it will be needed to introduce a buffer between the
Bandgap and the ADC. Thus, taking advantage from the characteristics of the buffer (low
output impedance, high input impedance and unitary gain) the system will be capable of
recover from the perturbations introduced by the ADC in the reference voltage.
Therefore, in this thesis are studied some of the already existing architectures of buffers,
in order to see the advantages and disadvantages of each one. This way were chosen the
best three architectures from a theoretical point of view, to implement and simulate, to
obtain all the needed information in order to better compare them
Dielectric constants of Ir, Ru, Pt, and IrO2: Contributions from bound charges
We investigated the dielectric functions () of Ir, Ru, Pt,
and IrO, which are commonly used as electrodes in ferroelectric thin film
applications. In particular, we investigated the contributions from bound
charges (), since these are important scientifically as
well as technologically: the (0) of a metal electrode is one of
the major factors determining the depolarization field inside a ferroelectric
capacitor. To obtain (0), we measured reflectivity spectra of
sputtered Pt, Ir, Ru, and IrO2 films in a wide photon energy range between 3.7
meV and 20 eV. We used a Kramers-Kronig transformation to obtain real and
imaginary dielectric functions, and then used Drude-Lorentz oscillator fittings
to extract (0) values. Ir, Ru, Pt, and IrO produced
experimental (0) values of 4810, 8210, 5810, and
295, respectively, which are in good agreement with values obtained using
first-principles calculations. These values are much higher than those for
noble metals such as Cu, Ag, and Au because transition metals and IrO have
such strong d-d transitions below 2.0 eV. High (0) values will
reduce the depolarization field in ferroelectric capacitors, making these
materials good candidates for use as electrodes in ferroelectric applications.Comment: 26 pages, 6 figures, 2 table
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