Measuring Noise of Low-Fixed-Gain Differential Amplifiers

Measuring noise of low-gain differential amplifiers presents a challenge, as their integrated feedback and gain resistors preclude high-gain configurations, and a differential-to-single-ended conversion is needed to match the spectrum analyzer. A second amplifier stage can provide gain and the differential-to-SE conversion, neatly solving both of these problems.

Detecting Human Falls with a 3-Axis Digital Accelerometer

Elderly individuals can suffer accidental falls due to weakness or dizziness. The initial injury can be further aggravated if treatment is not obtained within a short time. MEMS-based fall detectors can sense changes in body position by tracking acceleration, determine when an individual is falling, and issue an alert for assistance. This article describes the use of an ADXL345 three-axis digital accelerometer as a fall detector.

What shall we do with an unused op-amp?

Rarely Asked Questions -- Strange but true stories from the call logs of Analog Devices. View current and archived Rarely Asked Questions at http://www.analog.com/raq

Designing with Switching Regulators in High-Speed A/D Converter

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Automated Calibration Technique Reduces DAC Offset to Less than 1 mV

The AD5360 16-bit, 16-channel DAC is factory trimmed, but an offset of several millivolts can still exist. This idea shows how a simple software algorithm can reduce an unknown offset to less than 1 mV. This technique can be used for factory calibration, or for offset correction at any point in the DAC’s life cycle.

Digital Isolator Simplifies USB Isolation in Medical and Industrial Applications

Despite its low speed and point-to-point nature, RS-232 was tolerated in medical and industrial applications because it was universally available, well supported, and allowed easy implementation of the required isolation. The ADuM4160 digital isolator allows simple, inexpensive isolation of full- and low-speed USB peripherals—including the D+ and D– lines—increasing the usefulness of USB in medical and industrial applications.

Understanding and Optimizing Sampled Data Systems (Part II)

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Next topic: Understanding and Optimizing Sampled Data Systems (Part II)
Wednesday, May 20, 2009, 12:00 PM ET

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Accelerometers—Fantasy & Reality

High sensitivity, small size, low cost, rugged packaging, and the ability to measure both static and dynamic acceleration have made numerous new applications of surface micromachined accelerometers possible. Many of these were not anticipated because they were not thought of as classic accelerometer applications. New applications are limited only by the imagination of designers.

“Rules of the Road” for High-Speed Differential ADC Drivers

Most modern high-performance ADCs use differential inputs to reject common-mode noise and interference, increase dynamic range by a factor of two, and improve overall performance. ADC drivers—circuits often specifically designed to provide differential signals—perform many important functions including amplitude scaling, single-ended-to-differential conversion, buffering, common-mode offset adjustment, and filtering.

Volume 42, Number 4, 2008 Print Edition

In This Issue:

2 -- Editors’ Notes
3 -- Analog Front End for 3G Femto Base Stations Brings Wireless Connectivity Home
8 -- Considering Multipliers (Part 1) [The Wit and Wisdom of Dr. Leif—7]
15 -- Design, Simulate, and Document Proprietary Wireless Systems
18 -- Tales From the Back Burner
19 -- Product Introductions

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Notch Filter Reduces Amplifier Peaking and Increases Gain Flatness

Although the ADA4817 is unity-gain stable, a high-frequency pole increases its GWP from 410 MHz at high gains to 1 GHz at unity gain, while decreasing its phase margin. Adding a discrete RLC notch filter maintains the high bandwidth and input impedance, while dramatically reducing peaking, increasing gain flatness, and reducing overshoot.

Skin Impedance Analysis Aids Active and Passive Transdermal Delivery

Pharmaceutical firms are developing alternatives to injections. Transdermal methods, which feature noninvasive delivery of medication through a patient’s skin, overcome the protective barrier in one of two ways: passive absorption and active penetration. Skin impedance analysis facilitates proper dosing.

PLC Evaluation Board Simplifies Design of Industrial Process-Control Systems

The applications for industrial process-control systems range from simple traffic control to complex electrical power grids, from environmental control systems to oil-refinery process control. The intelligence of these systems lies in their measurement and control units. The two most common computer-based systems to control machines and processes are programmable logic controllers and distributed control systems.

Reconstruct a DAC Transfer Function from its Harmonic Spectral Content

DAC output spectrums contain harmonic content due to their non-ideal transient and static behavior. This article defines a method for deriving the DAC transfer function from the observed harmonic content, assuming that the static errors, rather than the transient characteristics, are the dominant source of the distortion.

Analog Microcontroller Forms Heart of Low-Cost, High-Efficiency PA Monitor

Saving energy is crucial for efficient wireless network operation. Power amplifiers (PA), the core of base stations and repeaters, can account for more than half of their total power consumption. Monitoring and controlling the PA can: improve efficiency and reduce operating costs; maximize output power and achieve the highest possible linearity; and allow the system operator to discover problems and improve reliability.

This Should Work: Thermistor Senses Liquid Levels

In precision temperature measurement applications using thermistors, RTDs, or other resistive temperature sensors, care must be taken to avoid self-heating errors caused by the excitation current. In some applications, however, the self-heating effect can be put to good use. The design concept presented here should work, but it has not been fully tested.

Power Boost Circuit with Current Sense and Kelvin Connection

In automatic test equipment, low-current adjustable and high-current fixed voltage sources are available. An additional supply must be created when a high-current adjustable voltage source is required. This article shows how a high-current rail-to-rail op amp boosts the current of an adjustable voltage source.

Using MEMS Accelerometers as Acoustic Pickups in Musical Instruments

MEMS microphones have begun to dominate the broad consumer market, including cell phones, Bluetooth headsets, personal computers, and digital cameras. Now, key technologies used in MEMS accelerometers can bring a new dimension to acoustic transducers. Low-g accelerometers don't suffer from traditional feedback problems, and show clear potential as high-quality acoustic pickups for musical instruments.