It is now trivial and non-invasive to measure blood-oxygen saturation SpO2, thanks to LEDs, algorithms, and ICs for pulse oximetry — and it’s a very long way from having to draw blood and send it out for assessment. Just a few decades ago, determining the vital medical parameter known as blood oxygen level — formally […]
basics
Quartz crystals and oscillators, Part 1: Crystal basics
An oscillator or clock function is key to nearly all electronic circuits, and in most (but not all) cases, the heart of this oscillator circuit is a tiny piece of quartz, called the crystal blank or slab. It’s easy and commonplace to think of the crystal as a simple component, but as with most components, […]
GPS, Part 2: Implementation
Part 1 of this FAQ looked at the basic principles of the GPS system. Part 2 looks at some hardware circuitry used to implement a GPS receiver as well as the unappreciated role that Einstein’s Theory of Special Relativity plays in providing an accurate GPS. Q What are the key elements of a GPS receiver? […]
GPS, Part 1: Basic principles
The Global Positioning System (GPS) is a worldwide, RF wireless-based system for determining where you are anywhere in the Earth’s surface if there is line-of-sight visibility to at least four of its orbiting satellites. The availability of GPS since its inception a few decades ago has not only enabled products and features which were simply […]
e-Fuses, Part 2: Building or buying an e-Fuse
The electronic fuse is a powerful and versatile tool in the designer’s kit, but building one requires careful selection of the core amplifier; IC embodiments solve the problem. Part 1 of this FAQ looked at the basic structure of the electronic fuse or e-fuse. This part looks at the requirements on the current sense amplifier […]
Why use an e-fuse? Part 1
The electronic fuse is a powerful and versatile tool in the designer’s kit, but building one requires careful selection of the core amplifier; IC embodiments solve the problem. The traditional thermal-based fuse, Figure 1, is a low-cost, widely used, well-understood, highly reliable, easy-to-apply circuit- protection component. It is available in a wide range of ratings, […]
20 mA current loops, Part 2: Advanced features
Part 1 of this FAQ looked at the basics of the 20-mA current loop, why it is still used extensively, and its primary attributes. In this part, we’ll look at how the analog current loop is used for digitized signals and at self-powered loops – two developments which have extended its life and viability. Q: […]
20-mA current loops, Part 1: Basic functions
You’ve been given an “easy” assignment: get the low-rate data from a temperature sensor to a control computer located 100 feet (30 m) away, in an industrial setting. After much investigation and assessment, you choose a widely used standard called the 20-mA loop, which has been in use for over 50 years, rather than Wi-Fi, […]
Electrical noise, Part 2: Additional perspectives
In Part 1, we looked at some facets of noise: sources, external versus internal (intrinsic) noise, and equations. Part 2 goes further into noise specifics. Q: What are some of the types of noise? A: It’s a long list. The same noise may have different names depending on the perspective of the person describing it, […]
Electrical noise, Part 1: Introductory concepts
Electrical noise is a consideration that engineers think, talk, worry, sometimes obsess about, and deal with nearly all the time, with few exceptions. In many applications, it is the limiting factor on ultimate achievable system performance. If it were not for the existence of noise, many design situations would be far, far easier. Noise is […]
