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 […]
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 […]
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 […]
Monotonicity: What is it and why is it important?
There are many parameters which define the performance of analog and mixed-signal circuits. Among the many “static” (sometimes called “DC” specifications, but this is a misnomer) factors are offset error, gain error, integral nonlinearity, and differential nonlinearity. Note that there are also dynamic specifications (called “AC” specifications but also a misnomer) such as the effective […]
Why use a nonlinear amp?
Users normally place a great deal of value in the high linearity of an amplifier and its corresponding low distortion. Audio amplifiers, for example, are quoted with many linearity specifications, such as total harmonic distortion (THD) or 1%, 0.1% or even less. Even the outputs of amplifiers with internal topologies which are inherently nonlinear, such […]
What does an analog driver/buffer do?
The term “buffer” has many definitions in electronics hardware and software. It can be a reserved software area where data is temporarily stored until it is processes; a set of internal IC registers where data is queued before being transmitted or after it has been received; or it can be a circuit function interposed to […]
Making sense of thermocouples and interfaces, part 2
Part 1 of this FAQ looked at the basics of thermocouples, where and why they are used, and some basic implementation issues; this part explores interface issues, cold junction compensation, and linearization. What are the requirements for thermocouple interface electronics? The thermocouple voltage is relatively small, so long leads between the thermocouple and the electronic front-end […]