Any unwanted signal that’s combined with the desired signal is called noise. In any circuit, noise can come from anywhere; from external systems as well as from within a circuit itself. External sources include a number of sources such as power lines, RF transmitters, nearby conductors, ignition systems, or motors that turn on and off […]
Reducing ringing or reflections by controlling impedance lines
What is a controlled impedance line? For one thing, the term has to do with Printed Circuit Board (PCB) traces and layouts, which get more complex with higher frequency signals. Generally, you need not worry much about controlling impedance in traces unless you are working with signals at or above 50 MHz. However, most of […]
Amplifiers: What do rail-to-rail and single supply mean?
With respect to analog signals, a “rail” is a boundary that a signal has to work within. For a long time, operational amplifiers have required opposite but equal voltage supplies. If you see a dual-supply or dual-voltage op amp, it means that two supply voltages power the amplifier; the absolute supply voltage levels are the […]
IBIS model: How can it help with signal analysis?
An Input Output Buffer Information Specification (IBIS) model is a standard in the semiconductor industry for modeling semiconductor devices from a behavioral perspective, for both analog and digital perspectives. IBIS modeling enables engineers to describe detailed signal behavior in a circuit design without revealing proprietary information about the circuits (or the processes used to make […]
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 […]
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 […]
Compensating for DAC Offset and Gain Error
Digital-to-analog converters (DACs) are subject to gain and offset error. Errors can be compensated for with hardware by using external components or by trimming the DACs after they have been manufactured. Trimming is necessary because the error is caused by mismatched resistors; trimming attempts to change resistor values in the DAC. However, some DACs can […]
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 […]
