編集後記

Welcome to the March issue of Analog Dialogue.

Outside of the world of analog, my son has recently introduced me to the book, blog, and YouTube channel The Big Bang, Outer Space and Life (Urknall, Weltall und das Leben) by professors Harald Lesch and Josef M. Gassner. The book explains complex astrophysics in a simplified yet scientific way. One fascinating topic is Betelgeuse (Alpha Orionis), a giant red star in the constellation of Orion that may be turning supernova. In the last few months, the light from Betelgeuse has decreased, turning from red to more of an orange color, and it fell from being the third brightest to the twenty-first brightest star in the northern hemisphere. Also, gravitational waves were detected from the same region by LIGO, the Laser Interferometer Gravitational-Wave Observatory, and innovative technology from ADI. This could be an indication that the star may turn supernova in the next few weeks, months, years—or even 700,000 years from now; scientists just aren’t sure when.

If you are interested in complex astrophysics explained in an easy way, I highly recommend subscribing to such a channel. If analog is more your speed, you can find more about LIGO and other technologies, electronic basics, new trends, evaluation platforms, and exciting topics explained by engineers on ADI’s YouTube channel. And now, back to Earth and the articles from Analog Dialogue.

Our Analog Dialogue starts with the topic of voltage references. This article explains the impact of a voltage reference to the accuracy of a high precision (>20 bits) data measurement system. To achieve this high resolution, a signal chain with exceptionally low noise is required. To provide perspective, to achieve 25-bit resolution, or 152 dB dynamic range, the maximum allowable system noise is 0.2437 µV rms. The voltage reference sets the performance limit that the ADC can resolve. Even the best standalone voltage references available in the market, with low noise specification, need some help to attenuate noise. External circuitry, such as a filter, can help attenuating noise achieve the desired ADC dynamic range.

Fluid-level measurements can be accurately measured through the wall of a nonmetallic tank by placing an air-dielectric transmission line up against the side of the tank and sensing the RF impedance. This article provides an empirical design example that illustrates how to simplify design by using a reflectometer such as the Analog Devices ADL5920. The reflectometer-based solution offers several benefits like fast, real-time fluid-level measurements, contactless design without liquid contamination, or moving parts, and also—just as important—no holes in the tank for an internal sensor.

Next, the price of multilayer ceramic capacitors (MLCCs) has risen sharply over the past several years. Ceramic capacitors are used in power supplies on the output to lower the output ripple and to control output voltage overshot and undershot due to high slew rate load transients. The input side requires ceramic capacitors for decoupling and to filter EMI due to their low ESR and low ESL in high frequency. The total cost of output ceramic capacitors can be several times that of the power IC. Higher power supply switching frequencies can reduce the effect of transients on output voltage and reduce the capacitance requirements and overall solution size. The monolithic Silent Switcher® 2 buck regulator family enables compact solution size, high current capability, high efficiency, and more importantly, superior EMI performance. In this article, the LTC7151S monolithic buck regulator with Silent Switcher 2 architecture is shown to simplify EMI filter design.

The next topic is fun with WAV files using LTspice®. LTspice has many superpowers, but its handling of audio files is one of its more impressive capabilities. LTspice can be used to generate WAV files as an output of a circuit simulation, as well as to import WAV files to excite a circuit simulation. It is well documented that mono WAV files can be used as an input in LTspice, and LTspice can be used to produce a WAV output. This article details how to use LTspice audio WAV files for the lesser known syntax of stereo and higher channel count.

In this month’s StudentZone article, we continue with the topic of op amps. One op amp specification is settling time. The settling time of an amplifier, or any signal chain for that matter, is defined as the time it takes the output to respond to a step change in the input and come into and remain within a defined error band around the final value. It sounds a bit complex, but is important to understand. Get your breadboard ready for the new lab activity from Antoniu and Doug.

And as we have for 54 years, we invite you to be part of the dialogue in Analog Dialogue. You can get in touch through our blogFacebook page, or email. Let us know how we’re doing and what you’d like to see from us in the coming months.