Analog Hotspot

Communications channels used to be a challenging exercise in pure analog design. Today, modulation occurs in the digital domain in many systems. But the transmitted signal is analog, so there’s always a conversion. For any communications system, choices for the digital- to-analog converter (DAC) and its current-to-voltageconverting op amp depend on the required bandwidth. As DACs and op amps get faster, they move closer to the transmitting...

Single Chip Digitizes High-Side Power Measurements In-circuit power measurements frequently involve a currentsense amplifier or a hot-swap controller and an analog-todigital converter (ADC). Optimally, the current sensing is done on the high side of the load to avoid false grounds. But one problem with that approach is the presence of a high common-mode voltage on the amplifier input. Another is the typical ADC’s limited input voltage range. In addition, the cost of...

There are now two sources of analog front ends (AFEs) for ultrasound applications. Texas Instruments is sampling the AFE5805, the first member of a future family for portable to high-end ultrasound diagnostic equipment. Last year, Analog Devices introduced the AD9271 for the same market. Functionally similar, both are octal devices that incorporate a lownoise amplifier, variable gain amplifier (VGA), anti-aliasing filter, and 12-bit analog-to-digital...

Download the full article as a .PDF, sponsored by Analog Devices What is class D amplification? Class D amplifiers are a more efficient alternative to class AB (push-pull) power amplifiers for audio signals. Class D is particularly attractive in portable applications because it helps extend battery life. Complete 3-W class D amplifiers are now...

HI BOB: I would like to ask about designing a sinewave amplitude attenuator with programmable attenuation. Preferably, it will just contain basic components (op amps, transistor, resistors, caps, etc.). Input: 1-V p-p sine wave (1 kHz frequency), symmetric at 0-V level. Desired output: still at 1 kHz, but the amplitude varies from 0 to 1000 mV. –JOERICH SUNICO HELLO,...

Few things are more frustrating than a requirement for some feature that exceeds the ability of your present hardware. Say you’re designing a product that has historically required an 8-bit digital-to-analog converter (DAC). Conveniently integrated on the system microcontroller, the DAC has never been a problem until marketing suddenly insists that it is absolutely necessary for the DAC to output 10 bits. Of course, it’s too late to change microcontrollers, and...

The highest demand and the most vigorous competition between companies that make analog-todigital converters (ADCs) lie in the sampling range from 50 to 65 Msamples/s in 10- and 12-bit resolutions. Market demand is highest for eight- and 10-channel devices with the lowest possible power consumption per channel. In late January, within days of each other, Texas Instruments and National Semiconductor announced groundbreaking new chips for that market...

Sensor measurements typically translate physical phenomena of interest into electronic-circuit parameters such as resistance and capacitance, which can then be read with a bridge circuit. Bridge circuits produce an output voltage or current signal that is ratiometric with respect to temperature and powersupply voltages, thereby enabling the measurement system to be immune to these variables. Sensor examples can include: Thermistors for temperature...

The MAX9516 video amplifier from Maxim Integrated Products doesn’t just detect and report the presence of a video load. It also reduces power consumption when the load isn’t present so system designers can better manage power (see the figure). On top of that, additional features further reduce power consumption in the system. Designers who use have used traditional video amplifiers have had to add an...

Stereo systems for multiple speakers put the left and right speakers on opposite sides of the room. Personal systems use left and right ear buds or headphones to separate the sound. What can designers offer in the way of stereo on a cellular handset or other compact personal listening device that uses speakers? Maxim Integrated Products says its highly efficient MAX9775 class D audio subsystems are the answer. They enable the use of wave interference to cancel...

Bob: While my full-time job is writing for Electronic Design, I still teach part-time and work on an NSF grant that is attempting to update the electronics curricula in community colleges. From my observations in my own college and across the country, most curricula are out of date with what is going on in the industry. (True, but not disastrously bad. We canâ??t ask that education for techs or for EEs be really up to date. That has almost always...

Once upon a time, op amps didn’t swing very close to the positive or negative rails. Even a couple volts away from the rails—that was okay in the old days of transistor-ized op amps. Hey, that was a lot better than with vacuum-tube op amps that wouldn’t swing within 200 V of the rail. Some op amps could do a little better, but customers never asked us for better 35 years ago. The LM324 can swing pretty close to ground (–VS) if you have a...

The thing about selecting the â??bestâ?? in mixed-signal chips lies in answering a key questionâ??best for what? Designers can calculate the analog-to-digital converter (ADC) figure of merit (FOM), based on power consumption, effective number of bits (ENOB), and sampling frequency. But interpreting an expression for pJ/conversion doesnâ??t really say anything about an ADCâ??s appropriateness for an actual application. THE...

Bob: In “What’s All This Capacitor Leakage Stuff, Anyhow?” (March 29, 2007, ED Online 15116) you have a diagram of a test circuit using the LMC662. This circuit is quite a bit different from the “capacitor soakage” test circuit you referenced on your Web site. (After you get the capacitor charged up, and after you get the soakage elements charged up (which takes hours and days), the rate of change of VOUT is caused by the leakage, which you cannot really see until...

Why the fresh emphasis on low-noise amplification? Some of it is an issue of signal-to-noise ratio (SNR). Today, sensor voltages and device operating voltages are lower than they used to be, so noise is larger in relation to signal levels. Another factor is that the data converters being used have higher resolutions than in the past, so they need cleaner inputs. What kind of noise are we talking...

Originally deployed for 1-Gbit Ethernet, a lot of existing fiber-optic cable could manage 10 Gbits/s, thanks to IEEE 802.3aq 10GBase-LRM (long-reach multimode). This standard was approved in 2006 to address multimode dispersion in legacy fiber with a technology called electronic dispersion compensation (EDC). Previous chip sets have depended on amplifiers that were less than optimal for the new standard. But Inphy’s 1348TA S03D transimpedance amplifier (TIA)...

Working in extreme temperatures or at high voltages in factory process control, distributed control, and smart transmitter applications can be tough for 4- to 20-mA current-mode transmitters and analog I/O systems. Yet four 12- to 16-bit single-channel digital-to-analog converters (DACs) from Analog Devices can make those jobs easier. These DACs integrate user-programmable current-source or voltage output. This makes them attractive because it...

Isolation is a means of preventing current from flowing between two communicating points. Typically, isolation is used in two situations. The first is where there's the potential for current surges that may damage equipment or harm humans. The second is where interconnections involve different ground potentials and disruptive ground loops must be avoided. In both cases, isolation is used to prevent current flow, yet allow for data or power flow between the two points. ...

Bob: As we were landing at O'Hare Airport last week, I was observing the runway and taxiway lighting. I immediately noticed that the lights are now LEDs. Would you believe that even these are designed to operate off the standard 6.6-A constant current system? (See www.flightlight.com/airportlighting/ 1.1/1.1.2.html.) This fixture is rated at only 3 W, which means it apparently drops 0.5 V at 6.6 A (perhaps 1.0 V or more with transformer losses?). There is still a power...