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JFET-based dc/dc converter operates from 300-mV supply
Use a JFET's self-biasing characteristics to build a dc/dc converter that operates from power sources, such as solar cells, thermopiles, and single-stage fuel cells.
You use a JFET's self-biasing characteristics to build a dc/dc converter that operates from power sources such as solar cells, thermopiles, and single-stage fuel cells, all of which deliver less than 600 mV and sometimes as little as 300 mV. Figure 1 shows the drain-to-source characteristics of an N-channel JFET under zero-bias conditions, which you can produce by connecting its gate and source together. Applying 100 mV causes a current of 10 mA to flow through the device, increasing to 30 mA at 350 mV. Exploiting the JFET's ability to conduct significant current at zero bias makes it possible to design a self-starting, low-input-voltage converter....
High-speed, 5-V amplifiers optimized for high-resolution video
Accurate high-resolution video reproduction places exceptional demands on the frequency response of video amplifiers.
Video op amps (like the good engineers who design with them) are constantly being asked to do more with less. To enable higher video resolution, higher analog-video signal bandwidths are required, demanding ever-faster amplifier products. At the same time, designers are looking for ways to achieve these higher resolutions with lower voltages and even single-supply rails....
High Performance Active Mixer Overcomes RF Transmitter Design Challenges
ext generation cellular base station transmitter design imposes significant challenges for RF designers. These wireless systems have stringent requirements for transmission of a clean signal with a low noise floor and low intermodulation and harmonic distortion. It is particularly challenging, as higher order modulation is required while transmitting multiple carrier signals. Demand for mixer linearity performance is high. In the past, passive diode-ring type mixers have been the devices of choice to meet these requirements....
Use a switching-regulator controller to generate fast pulses
Switching-regulator-controller ICs can deliver gate-drive pulses with rise and fall times of less than 2 nsec, making them ideal candidates for laboratory pulse-generators.
A source of pulses with fast-rising edges that approximate the step function can help you perform many useful laboratory measurements, including characterization of coaxial cables' rise times and location of cable faults using time-domain-reflectometry methods. For example, evaluating the rise time of a 10- to 20-ft-long RG-58/U cable requires edge-transition times of 1 to 2 nsec....
Low-Power, 12-Bit, 250-Msample/s ADC Offers 1.2-GHz Analog Input Bandwidth
Linear Technology has pushed sampling rates for its 12-bit analog-to-digital converter (ADC) family for high-IF applications to 250 Msamples/s while holding the chip's power consumption to a modest 740 mW at 2.5 V. Analog input bandwidth for the LTC2242-12 is 1.2 GHz....
EDN 16th annual Innovation Awards
WINNER: "Minimizing switching-regulator residue in linear-regulator outputs," By Jim Williams
Designers frequently use linear regulators to postregulate switching-regulator outputs. The benefits of this approach include improved stability, accuracy, and transient response, along with lower output impedance. Ideally, markedly reduced switching-regulator-generated ripple and spikes would accompany these performance gains....
WINNER: LTM4600 high-power dc/dc micromodulex
Linear Technology's LTM4600 is the first high-power dc/dc module that meets the spacing and assembly requirements of densely populated boards such as advanced embedded systems. This encapsulated µModule dc/dc power supply is housed in a 15×15×2.8-mm LGA package. The size of this complete power supply is smaller than most FPGAs and processors. With only a 2.8-mm profile, the LTM4600 can be placed on the backside of a board without adding significant thickness to the end product....
High IF sampling 12-bit ADC consumes considerably low power
Product of the Month - RF Design
To offer an upgrade path to higher sampling rates with considerably low power dissipation, Linear Technology has readied a 12-bit 250 Msps high IF sampling analog-to-digital converter (ADC) that offers a 1.2 GHz analog input bandwidth along with the lowest power consumption in its class. Designed for digitizing high-frequency, wide dynamic range signals, it is aimed at wired and wireless broadband communications applications. Its ac performance includes 65.3 dB signal-to-noise ratio (SNR) and 80 dB spurious-free dynamic range (SFDR) for signals up to 140 MHz....
Optimizing gate timing with external FET driver for high-input-voltage step-down converter
Reconfigure a circuit to extend input-voltage range
Many industrial applications require a non-isolated, low-voltage supply from a high-voltage input. To extend the input-voltage range of a regulator that could not normally accept the high input-voltage, high-voltage external MOSFET drivers can be used....
High-performance delta-sigma ADCs ease the limitations of embedded converters
As IC technologies have progressed towards higher integration, the realization of complete systems-on-a-chip (SoC) has replaced the discrete components that once populated boards. The benefit of such systems is reduced system cost, increased reliability, and decreased size....
Signal conditioning for high-impedance sensors
Maintaining accuracy in circuits that process signals from high-impedance sensors presents unique challenges. First, you need to identify when to use special design techniques. Then, you must choose devices that buffer and protect the sensors and circuits without destroying their accuracy.
If you had the option, you probably wouldn't use high-Z (high-impedance) sensors. Their sensitivity to external noise, solder-flux residue, particle tracking, bias currents, and distant charges can make repeatable measurements difficult. High-Z sensors have an upside, though: They don't self-load, and they inherently use little power. For certain variables, such as pH, light, acceleration, and humidity, the most practical sensors are high-Z devices......
µP-Controlled Oscillator Delivers Rock-Bottom Distortion
Function generators often play a critical role in the design, testing, and operation of encoders, modulators, demodulators, and measurement instruments. Here's an inexpensive way to build a bus-controlled sinewave oscillator that has downright low distortion. ......
Fast, simple one-shot pulse stretcher detects nanosecond events
A pulse stretcher makes high-speed, one-shot pulses compatible with the much-slower processor input.
Resolving fast events, such as pulses from a photodiode or transistor avalanche, requires a detector with enough bandwidth to handle the pulse. The LT1711 high-speed comparator can switch in 4.5 nanoseconds in response to such events, due to its nanosecond rise time and propagation delay, but what if information needs to be relayed to a microprocessor or DSP that is unable to resolve such short-duration events......
Digital Power Is Mostly Analog
Digital power is quite the buzz these days. Let's take a moment to examine the term. The simplest definition of “digital power” is the control of a switching regulator via a digital interface. This could include, for instance, controlling the output voltage, switching frequency or sequencing of a multiple-channel supply via an I2C or similar digital bus. Start-up, margining, power-up and power-down sequencing can all be controlled via a digital signal or signals. This is quite feasible with today's technology, and many power management ICs today operate in this manner: analog switching regulators controlled via a digital interface......
Minimizing switching-regulator residue in linear-regulator outputs
Banishing those accursed spikes takes attention to detail and understanding the subtleties.
Designers frequently use linear regulators to postregulate switching-regulator outputs. The benefits of this approach include improved stability, accuracy, and transient response, along with lower output impedance. Ideally, markedly reduced switching-regulator-generated ripple and spikes would accompany these performance gains. In practice, all linear regulators encounter some difficulty with ripple and spikes, particularly as frequency rises. The regulator's small input to output differential voltages magnify these effects; this situation is unfortunate, because such small differentials are desirable for maintaining efficiency......
