Part 1 looked at the basics of RS-232. This part continues that examination, along with some extensions to the standard and test issues. Q: What are some of the issues associated with RS-232 and its performance? A: The standard allows for many user choices in how the DTE and DCE are configured: number of data […]
RS-232 and related standards, Part 1
High-speed, high-performance “just plug and go” wired-communications interfaces such as Ethernet and USB are in wide use. In contrast, the technically ancient RS-232 standard and related standards seem like antique museum pieces with no design-in interest. However, that is a simplistic view of the reality. Although not necessarily the first choice or obvious choice in […]
Solenoids and relays, Part 2
Part 1 looked at the solenoid, an electromechanical component which translates applied current into linear motion. The design of the electromechanical relay uses a coil and current drive (or a voltage source) just as with the solenoid. However, the function of the relay is quite different. Despite the availability of alternatives for some applications such […]
Solenoids and relays, Part 1
Just hearing the words “solenoid” and “relay” may conjure up visions of an ancient electromechanical word, now largely replaced by all-electronic devices, smart motors, and more. That almost makes sense, as these two components in various forms have been with us for over 150 years. But don’t be fooled: both are still vital devices, and […]
Fuses for power protection, Part 1
Fuses are the oldest and easiest-to-understand circuit-protection components, with several common schematic representations, Figure 1. The function of the fuse is simple and clear: in the case of an overcurrent condition, the fuse “opens” (or blows, in common parlance) which thus stops the flow of current. Despite their simplicity, fuses have subtleties and considerations which […]
Current feedback amplifiers, Part 2
Part 1 of this FAQ look at the operation of the CFB op amp and compared it to the VFB op amp. Part 2 continues the discussion of these two op amp topologies and their characteristics. Q: How do you choose between VFB versus CFB? A: Today’s CFB and VFB amplifiers have comparable performance, but […]
Eye and Constellation Diagrams, Pt 2
Part 1 looked at the eye diagram, a simple yet powerful visual tool which reveals many specifics about the quality of a recovered bit stream. Part 2 looks at the constellation diagram, another powerful visual tool which is used to show the signal space of complex encoding schemes and relationship among the symbols. Q: Why […]
Eye and Constellation Diagrams, Pt 1
Digital signals representing data symbols may be presumed to be clean, consistent representations of ones and zeroes when they are launched onto their communications medium, whether it is a wired, wireless RF, or optical fiber link. However, due to bandwidth limitations of the medium, external and internal noise, crosstalk, multipath, reflections, and many other unavoidable […]
Impedance matching and the Smith chart, Part 2
Part 1 looked at impedance matching and the need for a complex conjugate impedance at the load, compared to the source impedance. Once the need for an impedance-matching network is determined – and it is very likely needed – the next challenge is defining and creating this network. It may seem that doing a few […]
Impedance matching and the Smith chart, Part 1
In circuit designs spanning low-frequency audio through high-frequency RF, there’s considerable discussion about impedance matching between components or subcircuits, with various tools such as the Smith chart with is used to facilitate the matching. Q: What is impedance matching? A: Impedance matching means that a signal source sees a load impedance which is the complex […]
