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This paper proposes a feedback time difference amplifier (FTDA) that achieves linear, controllable gain and changeable input range for different time difference gains. The proposed FTDA consists of two identical feedback output generators. The feedback output generator achieves a linear input–output transfer characteristic by employing two p-type keepers for time gain feedback control. Its validity was demonstrated using $${0.13}\, {\upmu \hbox {m}}$$ SiGe BiCMOS process. The power consumption is $$91.54 \,{\upmu \hbox {W}}$$ for the highest gain with input signals at $${2}\,\hbox {MHz}$$ . The gain can be controlled from 25.06 to $$734.9\,{\hbox {s/s}}$$ within $$40 \,\hbox {ps}$$ input time interval.

An insulated-gate bipolar transistor (IGBT) pulse generator for repetitive transcranial magnetic stimulation used for in vivo laboratory experiments on small animals, such as mice, is reported. The pulse generator is based upon an IGBT that can switch 700 A of current for 1 ms and that has a DC breakdown voltage of 1200 V. The duration of the design's output pulse is controlled by, and follows, an input trigger pulse. The voltage amplitude of the output pulses is determined by an external high-voltage power supply and the energy stored in a 330 µF capacitor bank. The approach enables the amplitude of the voltage applied across the coil, the length of time the voltage is applied, and the number of times the voltage pulses are applied all to be controlled and adjusted to facilitate a wide range of experimental options. This paper provides a detailed schematic of the design, design discussions, and some representative experimental results. Additionally, the reported design can be scaled to higher currents by using an IGBT with a higher current rating.

An intelligent EWOD top plate control system is proposed in this study. The dynamic top plate is controlled by a piezoelectric (PZT) cantilever structure. A High resolution laser displacement sensor is used to monitor the deflection of the top plate. The gap height optimization and the top plate vibration significantly improve the droplet velocity and decrease the droplet minimum threshold actuation voltage. The top plate vibration induced actuation velocity improvement is magnitude and frequency dependent. 100 μm and 200 μm vibrations are tested at 25 Hz. Vibration frequencies at 5 Hz, 10 Hz, and 20 Hz are tested while the magnitude is 200 μm. Results show greater improvements are achieved at larger vibration magnitudes and higher vibration frequencies. With a vibrated top plate, the largest reduction of the actuation voltage is 76 V RMS for a 2.0 μl DI water droplet. The maximum droplet instantaneous velocity is around 9.3 mm/s, which is almost 3 times faster than the droplet velocity without top plate vibration under insufficient driving voltages. Liquid that has different hysteresis such as acetonitrile with various concentrations are used as a control to show its compatibility with the proposed DMF chip. Contact line depinning under top plate vibration is observed, which indicates the underlying mechanism for the improvements in actuation velocity and threshold voltage. The top plate control technique reported in this study makes EWOD DMF chips more reliable when used for the clinical point-of-care diagnostic applications.

Links at 1 micron offer key advantages over longer wavelength links. Both ultra-stable, low noise Nd:YAG lasers and high power efficiency, temperature-stable GaAs lasers operate at wavelengths around 1 micron. These components are particularly beneficial for quantum optical systems and links which require stability over a wide range of temperatures, such as are required in avionics. However, a key component missing in these 1 micron photonic links is a high-power photodiode receiver with high linearity and high quantum efficiency. Freedom Photonics and the University of Virginia have collaborated to develop photodiodes which fill this need. The photodetectors are based on an optimized vertically illuminated modified uni-traveling carrier (MUTC) photodiode technology. We report devices with quantum efficiencies in excess of 80% at 1064 nm, with a 3-dB bandwidth of 28 GHz, for a 20µm diameter device. The same device size handles very high power, with a 1-dB compression of >16 dBm RF power at a 64-mA photocurrent. These photodiodes have a major impact on peak performance of a photonic link, supporting high link gain and large bandwidths. Additionally, the high linearity of these devices minimizes noise and signal distortion, maximizing spurious-free dynamic range (SFDR). These are the first photodiodes of this type which have been packaged and made commercially available for this target wavelength.

Very-large-scale integration (VLSI) is a term used to describe integrated circuit designs using thousands, or more, of field effect transistors (FETs) [Mead79]. VLSI chips can be implemented using several methods, including gate arrays, standard cells, and full-custom design [Baker08]. In this short tutorial, we will focus on full-custom design or design at the transistor level. We will use complementary metaloxide semiconductor (CMOS) technology that includes an n-type metal-oxide FET, n-type MOSFET or NMOS for short, and a p-type MOSFET or PMOS.

An externally triggered analog sampling circuit used as an alternative to a high speed analog-to-digital converter (ADC) in microcontroller systems is designed, fabricated and characterized. High speed ADCs are expensive in terms of cost and power dissipation, the fast transient digitizer (FTD) is a low cost alternative and has no appreciable DC power dissipation. The transient digitizer uses cells with a process dependent delay element to sample data onto hold capacitors. The hold capacitor drives a PMOS source follower that is activated by an NMOS switch. The switch is controlled by on-chip logic that reads each sample sequentially in conjunction with an external counter. The FTD can capture an input signal with a maximum duration of 25 ns and an input range of 0 V to 2 V. The output is a reconstruction of the input signal on a timescale up to a few hundred μs. Two FTD circuits are fabricated on a 1.5 mm × 1.5 mm die using a 500 nm CMOS process; one FTD circuit occupies an area of 1.057 mm × 0.461 mm on the die.

This paper describes a feedback time difference amplifier (FTDA) with good linearity and high gain for coarse-fine time-to-digital converters. The symmetrical FTDA has two identical output generators. Each one consists of one SR-latch, one XOR gate, one buffer and two feedback P-type keepers. The improvement in linearity and time difference gain is achieved with two feedback paths based on meta-stability of the SR-latch. Its validity was demonstrated using 130nm CMOS technology. The power consumption is 91.54uW for the highest gain at 2MHz input signals. The gain can be controlled from 25.06 to 734.9 with a ±20ps input time interval.

A grid-tied photovoltaic (GTPV) in conjunction with the proper energy storage system, have the potential to increase electrical power quality and reliability. This paper highlights the key dynamics behind GTPV energy storage sizing. Brief assessments on the merits of energy buffers for solar GTPV are presented. Also presented is an economical framework that may help policy makers assess all the benefits in order to manage the trade-offs intrinsic to renewable technologies. Study results showed that 245Ah and 2.5 kAh buffers were needed to produce 6 kWh per day for 30 minutes and 60 kWh per day for 5 hours, respectively. Results also revealed that the “customer-generator” GTPV system has cut the electricity bills significantly down, 36.45 percent, throughout the study year.

Transient heat transfer analysis by means of analytical methods is known to be cumbersome. This paper seeks to develop an LTspice model of a real-world solar thermoelectric generation system. The thermal parameters of the proposed model were extracted from a multitude of parts' geometries and properties. These parameters were then converted into their electrical equivalences through the “thermal-to-electrical analogy.” In addition, real site data were fed into the Spice model via the built-in piecewise linear command in order to implement the real system's thermal behavior. An interesting RC analogy was derived from this model in order to demonstrate how thermoelectric generation systems respond to square wave-like solar radiation. Although temperature variations on the cold side of this LTspice model are roughly 80% accurate, simulation results and the actual experiment remain in good agreement.

A passive 2nd-order sigma-delta modulator using switched-capacitor based filters was designed, fabricated, and tested. A novel 2nd-order single feedback path topology is used. All circuitry is optimized for low power operation through the use of minimum size MOSFETs, component reduction and topology choice. The modulator was fabricated in On Semiconductor's C5 500-nm process. The implementation achieves a typical SNDR of above 50 dB for tested frequencies of 10 Hz to 3 kHz and has a peak SNDR of 57.8 dB, which corresponds to an ENOB of 9.3 bits. With a 2.5 V supply, the power consumption of the sigma-delta modulator is 6.75 μW. The modulator achieves a FOM of 1.78 pJ/step.

A highly efficient and reliable electrowetting on dielectric (EWOD) digital microfluidics (DMF) chip is proposed. An 8 μm parylene C layer is used as the dielectric material. Extra vapor-phase silane (VPS) is introduced into the chamber and acts as an aerosol primer to enhance the chemical adhesion to the parylene C surface. The EWOD chip can perform droplet dispensing, merging and splitting smoothly in an air ambient. Dual electrode dispensing mode (DEDM) and single electrode dispensing mode (SEDM) are tested to investigate the dispensing volume accuracy. Small deviations (0.0467 μL for DEDM and 0.0303 μL for SEDM) are observed for the dispensing. Droplets from 1.5 μL to 2.3 μL are tested for the minimum splitting voltage. Larger droplets require larger voltages to be split. The proposed EWOD chip is promising for future point-of-care clinical diagnostics.

The displacement of an intelligent PZT (piezoelectric materials based on modified lead zirconate titanate) controlled EWOD (electrowetting on dielectric) top plate is modeled by inverse Preisach hysteresis algorithm. First, the PZT deflection model is created from an experimental displacement dataset. The real time output is predicted based on the previously stored weighting functions. Upon the desired output and the current input, the input voltage is compensated by a feedforward voltage which is derived from the model using a closest match method. The feedforward process and the model are stored in a PC. A portable high voltage DAC (digital-to-analog converter) is used to drive the PZT cantilever structure. The worst-case DNL of the high voltage DAC is 0.8125 mV. The tracking errors of a 0.067 Hz triangle wave input are less than 5 μm. Results show the inverse Preisach model is a good candidate for precise EWOD top plate displacement hysteresis compensation.

Methods to mitigate the effects of power transients associated with grid-tied concentrated photovoltaic systems due to fast-moving cloud coverage were assessed. The approach was to buffer intermittency of concentrated photovoltaic output power with used electric vehicle batteries. The main goals of using grid-tied photovoltaic in conjunction with the proper energy storage (340kWh) were 1) to smooth out the intermittent solar power and 2) to defer part of the peak load to a convenient time with a proper control strategy. Real data from the summer of 2011 were utilized to conduct this study. Hence, simulation results showed that not only the unit was capable of putting a constant amount of power (20 kW) onto the grid, but also was able to shift the less valuable off-peak electricity to the on-peak time, when the price of electricity cheaper.

This issue of IEEE Solid-State Circuits Magazine recognizes, and pays tribute to, the 65th anniversary of the International Solid-State Circuits Conference (ISSCC). In addition, as usual, several articles of interest to IEEE Solid- State Circuits Magazine readers, ranging from tutorials to technology overviews, are included in this issue. These include popular columns and tutorials. The goal of the magazine continues to be to provide Society news and information as well as a series of selfcontained resources to keep the IEEE Solid-State Circuits Society member up to date with changes in technology while, at the same time, providing reviews of circuit design concepts. This includes contributions from experts describing the current state of affairs and evolution of a particular IC technology. We will also continue to feature articles focused on the contributions of luminaries.

An ultra-sensitive electrowetting on dielectric (EWOD) capacitance measurement system is proposed in this study. A 24-bit integrated circuit (IC) capacitance-to-digital (CDC) sensor is used to convert the capacitance changes caused by variations in droplet volume and concentration to digital data. A 2.3 mm by 2.3 mm printed circuit board (PCB) based electrode pair is used to sense the analog capacitance change. The capacitance of pure water and NaCl solutions are tested by the CDC system. Desktop-drawing software is used to fix the position of the droplet to obtain a small capacitance deviation of 10 IF. Result shows the CDC system can resolve the capacitance changes caused by adding 0.1 micro-liter droplets or by increasing the NaCl concentration by 1%. The digital output of the sensor is interface-friendly to microcontrollers.

A low-cost and high-resolution capacitive-to-digital converter integrated circuit is used for droplet position detection in a digital microfluidic system. A field-programmable gate array FPGA is used as the integrated logic hub of the system for a highly reliable and efficient control of the circuit. A fast-fabricating PCB (printed circuit board) substrate microfluidic system is proposed. Smaller actuation threshold voltages than those previously reported are obtained. Droplets (3 µL) are actuated by using a 200 V, 500 Hz modulating pulsed voltage. Droplet positions can be detected and displayed on a PC-based 3D animation in real time. The actuators and the capacitance sensing circuits are implemented on one PCB to reduce the size of the system. With the capacitive droplet position detection system, the PCB-based electrowetting on dielectric device (EWOD) reported in this work has promise in automating immunohistochemistry experiments.