Almost every engineer who has to deal with real-world signals, analog sensors, front-end circuitry, filtering, line drivers/receivers, or general amplification is familiar with the basic operational amplifier (op amp) which is the building block of most analog circuity. These op amps generally use voltage feedback (VFB), and have been studied and used extensively. However, there […]
basics
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 […]
Using the Smith Chart for impedance matching, 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 […]
Mechanical vibration for electronics: the quartz crystal
It is now 100 years since Alexander Nicholson at Bell Telephone Laboratories built and patented the first crystal oscillator, and crystals are still the main source of accurate oscillations up to UHF frequencies using quartz instead of Rochelle Salt (see US patent 2212845). Quartz crystal oscillators use the piezoelectric effect. The piezoelectric effect refers to […]
Analog switch vs. digital switch ICs
Analog switch integrated chips (ICs), when turned on, will conduct both analog and digital signals from the input pin to the output pin. Digital switches can only accept digital signals and duplicate the logic level on the input pin at the output pin. When the digital switch is turned off, it returns to a default […]
Analog comparators and hysteresis
A standard system requirement is to use the result of a simple “A vs. B” comparison as a basis for decision-making. For example, if the temperature is above a setpoint, turn the heat source off; and if the temperature is below that setpoint, turn the heat source on. Or perhaps there’s an alarm to sound […]
Nyquist rate basics and sufficient sampling for ADCs
Converting a real-world (analog) signal into a digital signal means that you have to bring the signal into an Analog-to-Digital converter (ADC). From there, the ADC turns the continuous analog signal into a discrete, digital signal by sampling, or taking regular snapshots of, the curves of the analog signal. After sampling is complete, any information […]
Selecting an op amp
You could start with a similar op amp from a similar, known-good circuit or reference design and extrapolate from there. However, not everything labeled a reference design has actually been built and tested. But there’s another way to get organized and feel in control of the selection process. A methodical approach is outlined below that […]