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 […]
FAQ
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 is a multiplying DAC?
Multiplying digital-to-analog converters (MDACs) produce a (current) output signal that’s a product of the given reference voltage and the code (i.e., a string of 0s and 1s) flowing through it. All data converters require a voltage reference (VREF) and a typical, standard DAC needs a very stable fixed reference voltage in order to operate properly. […]
Optocoupler selection and usage for isolating a PWM
An optocoupler (or optoisolator) is a device that galvanically separates circuits and is not only great at isolation but allows you to interface to circuits with different ground planes or that operate at different voltage levels. Optocouplers are “fail safe” in that if subjected to voltages higher than the maximum rating, they are known to […]
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 […]
Are your op amps pumped?
I was recently thinking about the issues surrounding rail to rail input opamps and the problems of making them low distortion – a problem I have had to overcome when designing integrated circuits for instrumentation applications. Some rail to rail opamps use two input stages – one using NMOS input transistors, the other using PMOS […]
Basics of bandpass filters
Filters will allow some signals to pass through while blocking others. A bandpass (a.k.a. band-pass) filter allows signals of a certain frequency range (“a band of frequencies”) to pass through the filter as-is. (This range of accepted frequencies is called the passband. The size or range of the passband is called the bandwidth.) With a […]
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 […]
Making sense of thermocouples and interfaces, part 1
Temperature is the most frequently measured real-world variable, and despite its age, thermocouples are still among the most-used temperature sensors. They are used in test and measurement equipment, instrumentation, and even in standard home ovens due to their low cost, reliability, simplicity, and ability to measure into hundreds of degrees. What is a thermocouple and […]
Unity gain amplifier or voltage follower in a voltage divider
A voltage follower is also known as a unity gain amplifier, a voltage buffer, or an isolation amplifier. In a voltage follower circuit, the output voltage is equal to the input voltage; thus, it has a gain of one (unity) and does not amplify the incoming signal. The voltage follower does not need any external […]