Analog Hotspot

The floods that hit the Northeast U.S. in April nearly wiped out one of the motherlodes of analog history. Thanks to heroic work, most of the documents at the David Sarnoff Library in Princeton were saved. But it took a major effort and donations from the IEEE, the Antique Radio Club of Illinois, and other private and institutional donors. To really appreciate the library, you have to be an alpha geek like my friend Charlie Osborn. Charlie got deeply involved with the...

Hello Bob: I'm designing wideband photodiode amplifiers and using Jerald Graeme's excellent book (Photodiode Amplifiers—Op Amp Solutions) as a reference. In the case of a composite transimpedance amplifier (TIA) discussed in Chapter 6, do you know whether the phase compensation requirement that dictates a value of CF for stability/gain peaking (i.e., the formula on page 58) changes? (Refer to my column "...

For professional digital audio recording and processing, Texas Instruments' PCM4220 and PCM4222 24-bit, 216-kHz delta-sigma analog-to-digital converters (ADCs) provide up to 124dB signal-to-noise ratio (SNR). While sampling at 48 kHz, these two-channel ADCs consume 305 mW, permitting designs that power computer audio interfaces entirely through a USB or Firewire bus. The 6-bit output from the delta-sigma modulators in the PCM4220 is routed to a digital decimation filter, whose...

EIA-485 (RS-485) may seem a little retro. But the standard is still the simplest way to drive digital data over long distances (i.e., 4000 feet) with multidrop capability. Recognizing this, Maxim Integrated Products' has come up with a pair of chips that simplify RS-485 implementations. The MAX13487E and MAX13488E half-duplex RS-485 transceivers achieve this simplification with a feature Maxim calls AutoDirection. This feature automatically enables the driver when transmitting...

Compared to single-ended signaling, differential signaling offers many benefits: less electromagnetic interference (EMI), less distortion, lower supply voltagei, and lower costii. These advantages have prompted the adoption of differential signaling in many applications, including digital (low-voltage differential signaling, or LVDS) and analog (audio). Similar benefits should accrue to analog videoiii. But for reasons that may no longer be valid, most video...

I sure walked into it. I've always known that I can stuff my warm feet (with warm socks) into frozen boots and just start walking, and they would warm up nicely. These are Vasque trekking boots, weighing about 2.1 lb each, well insulated down to about –20°F and extremely comfortable. So I put them on and hiked up the trail, all very cozy, on Jan. 17. The air temperature was around 10°F to 20°F—not bad. But after several hours, I got tired and needed...

Hi Bob: Your tip on how to phase a generator into the electric grid would work ("What's All This ‘Others Stay Lighted' Stuff, Anyhow?"). Phasing sets of the not too distant past used a couple of incandescent bulbs and a guy poised with his finger on the button, just as you said. I wanted to explain, however, that in the electric power industry, we go to great...

Industrial applications, which include arenas as varied as factory automation and automotive design, represent around 30% of the market for most ADC makers. Not surprisingly, ADC manufacturers are aggressively going after this market. Linear’s 1.5-Msample LTC2351-14 is a 14-bit ADC with an 83-dB CMRR and serial output for multiphase power measurement, multiphase motor control, data-acquisition systems, and uninterrupted power supplies. It simultaneously samples up to six...

News on the business front includes National Semiconductor’s acquisition of Xignal. A year and a half ago, this German startup used its experience with serializer/deserializer (SERDES) IP for a breakthrough in bringing continuous-time delta-sigma to market (see “‘Sample Wars’ And Silicon Technologies Energize ADCs”). Xignal’s initial product used a...

Analog-to-digital converters (ADCs)—the workhorses of the industry—have plowed their way through applications like industrial process control, medical instrumentation, communication systems, and radar for decades. Continual increases in performance specs have kept these blue-collar devices in step with the latest advances. February's International Solid State Circuits Conference (ISSCC) in San Francisco presented the cream of the ADC crop. A number of papers on...

We all know that capacitors have a shunt resistance (leakage) and that leakage resistance should be pretty easy to measure, right? Wrong! I've measured a lot of capacitors for short-term soakage (dielectric absorption) per www.national.com/rap/Application/0,1570,28,00.html. After the short-term soakage stops, it's possible (not easy) to measure the leakage. For example, if you charge a...

The most critical circuits in any radio design are the mixers and IQ modulators/demodulators as they establish the basic specifications for the entire product. Linear Technology's LT5557 down-converting mixer, LT5571 quadrature modulator, and LT5575 I/Q demodulator step up to tackle these challenges. The LT5557 targets 3G and WiMAX basestation receivers, power-amplifier (PA) linearization circuits, and wireless local-area network (WLAN) products. It incorporates a...

Hi Bob: I have been following your silicon-dioxide (SiO2) articles and just saw Steve Krueger's response ("Bob's Mailbox,") naming it under the trade name Cabosil. We use Cabosil at our company as a thickening agent for adhesives and epoxies during manufacture. When I had my first exposure to it, I was told it was small glass spheres. (There are some epoxies with air-filled...

It used to happen at the kickoff meeting for every new program. The engineer managing the development team would come in with an armload of overhead-projector transparencies for the business-unit managers and marketing people, who were there to learn about features, design challenges, schedules, resources—the usual stuff. Inevitably, about the third foil down, would be one of those triangle graphics with a bubble at each vertex (...

Hello Mr. Pease: I've read somewhere that it can be a problem for the op amp to lose one of the supplies or use the wrong startup sequence. (You are correct. A startup sequence can cause great trouble on the positive and negative rails. /rap) Is it always a particular rail? Can you shed some light on the cause of this? Does it apply for bipolar and CMOS families? • David Smith • Pease:...

The typical LCD backlight can be one or more cold cathode fluorescent lamps (CCFLs) or an array of light-emitting diodes (LEDs). The quality of the backlight image depends heavily on the backlight driver. This article discusses the considerations one can make for CCFLs and LEDs, as well as how to power both kinds of backlight...

Return paths The physical area created by the signal and return path determines the amplitude of energy that’s radiated unintentionally, so minimize the area of these return loops. Single-ended signals should be routed adjacent to a ground plane. Ground loops Multiple grounds are a necessary evil when circuits are functionally differentiated. You end up with small voltage potentials between the grounds...

Noise and jitter that affect bit error rate (BER) on high-speed data buses is one thing. But electromagnetic interference (EMI) is another, more traditional noise problem. EMI has become a problem for power-supply designers, now that efficiency has popularized switched-mode supplies. Chip manufacturers now make more applications information available to engineers who design using their chips. National Semiconductor provides layout recommendations specific to its LM3100 Simple...

Instruments such as those in LeCroy's Serial Data Analyzer (SDA) family measure jitter and create eye patterns based on the time difference between crossing points in the data stream and those of an ideal reference clock. This involves sampling at a high rate and processing a long record. Specifically, all of today's high-speed serial data standards require minimum sampling rates of 20 Gsamples/s and rise-time capabilities faster than 300 ps. Setting the phase-locked...

The war on noise now takes us into the next frontier: the high-speed serial backplane. Actually, this is about both noise and jitter, which is a practical approach, if not rigorously correct. Tektronix's Pavel Zivny likes to limit noise to "all things undesirable in the vertical (voltage, or power for optical signaling) direction," distinguishing it from jitter, "which is all things undesirable in the ‘horizontal,' i.e., time, direction." The problem is that it's difficult to...