Analog Hotspot

In my previous column, I took a historical approach to delta-sigma modulation with the single-slope converter (May 8, p. 18, ED Online 18747). Jim Williams of Linear Tech responded, and he sent me a copy of a 1949 article by D.H. Wilkinson on single-slope analogto- digital converters (ADCs). “I’m aware of their obvious weaknesses, but the simplistic elegance of the...

When I present seminars, I often ask the members of the audience to hold up their hands if they think bipolar op amps have better gain and linearity than CMOS. I get a good majority of hands. But neither is bad! The good-old LM301A (well over 30 years old) has a good gain of 260,000 at no load, with just 75 µV p-p of gain error while its output is swinging 20 V p-p (Fig. 1). What happens ...

According to Maxim Integrated Products, the MAX2065 fully programmable, multistate, analog and digital IF/RF variable-gain amplifier (VGA) aims to solve a number of automatic gain control (AGC) design problems in GSM/EDGE, CDMA, WCDMA, LTE, and WiMAX receiver applications (see the figure). But what does that mean? In explaining the thinking that went into the design of the...

Tuners for set-top boxes, DVRs, PC TVtuner cards, and the like keep getting simpler to design in and less demanding to assemble into end products. Anadigics’ AIT1032 1-GHz double-conversion tuner implements upconverter, downconverter, voltage-controlled oscillator (VCO), synthesizer, RF and IF amplifier, and RF and IF gain control functions with a combination of gallium-arsenide (GaAs) and silicon technologies. It’s designed to avoid...

Download the full article as a .PDF, sponsored by Analog What are digital potentiometers, and how are they used? Digital potentiometers are integrated circuits that implement a resistive ladder and a digital means of addressing a particular tap on the ladder that corresponds to the wiper position of a mechanical potentiometer. They’re used to...

HI BOB, I have been collecting some new but mostly museum-grade test instruments. Along with purchases from various instrument rental houses, flea markets, and so on, for a while I bid on items in government liquidation auctions. Occasionally, I won. The starting bid was always $50, and some I got at that price. Some went way higher but seldom approached the original list price, and I gave up way before that. Often, the shipping costs to a pickup and forward...

It’s possible to build a push-pull amplifier using amplifier ICs, rather than discretes, as in the traditional class B amp (see the figure). A bridged-amplifier configuration effectively doubles the voltage swing at the load. It’s also possible to build a bridge amplifier in which one stage drives one side of the speaker and a second unity-gain inverting amplifier drives the other side of the speaker. However, the...

Amplifiers are fundamental circuit-design elements. They drive everything from earbuds to antennas. Placed ahead of analog-to-digital converters (ADCs), they reshape signals from sources as diverse as strain-gauges to ultrasound probes. Through proper selection of feedback passives, they can be configured into high-pass, low-pass, band-pass, and band-elimination filters. Feed them with multiple signals, and they produce harmonic series of all the...

The mainstream media may call it a digital age. But today’s gadgets still need integrated circuits that can transform analog signals—which convey information about “real world” phenomena like temperature, pressure, sound, and speed—into digital form. Linear Technologies is one of the leading companies designing, manufacturing, and marketing a broad line of standard high-performance analog integrated circuits as well as devices that control power and regulate voltage in...

Download the full article as a .PDF, sponsored by Analog What are VGAs? Variable gain amplifiers (VGAs) are signal-conditioning amplifiers with electronically settable voltage gain. There are analog VGAs and digital VGAs, or DVGAs. An analog voltage controls the gain in both, which differ in how it is applied. A digital-to-analog converter ...

HI BOB, Any big trips to exotic spots planed this year? We’re headed for Newfoundland and Prince Edward Island for a change of pace. (I may go to Scotland in September. /rap) My question: Do you have some circuitry I could use for an electronic bagpipe simulator? It would need nine notes selected by removing fingers from some form of contact that would reasonably simulate a finger hole. I don’t need too many...

Suppose you were designing a digital camera, and you wanted to extend its battery life by turning off its big power-hungry display screen whenever its users have their eye up to the optical viewfinder. Or suppose you were designing a notebook and you wanted a feature that would turn the keyboard backlight on only when the user’s hands were near the keyboard. Or suppose you were designing a touchscreen phone and you wanted to deactivate the on-screen buttons when...

One day, back about 1966, I was going up the elevator at 285 Columbus Avenue in Boston to look at some production problems on Philbrick’s fifth floor. And who was in the elevator, but George Philbrick’s friend Jim Pastoriza. Jim was going up to show George his new analog computer demonstrator—portable and battery-powered. In fact, it was running, and he gave me a demo right on the elevator as we ascended. And, this modular analog computer ran on a couple of...

As an application engineer, I spend a lot of time convincing customers that a delta-sigma modulating analog-to-digital converter (ADC), or DSM, would be the best choice for their particular application. Then they come up with all sorts of excuses for why they prefer a successive-approximation ADC. I’ve come to the conclusion that they prefer successiveapproximation ADCs because they fundamentally don’t understand how a DSM works, perhaps because DSMs involve...

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...