Glossary of EE Terms


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  • Safety Isolation

    Isolation that protects people or equipment from shock that may occur during failure of a circuit that includes high voltage.

  • Sample Rate (MSPS)

    Sample Rate is the number of conversions per second the DAC is producing.

  • Sampling Frequency

    The sampling rate, sample rate, or sampling frequency, defines the number of samples per unit of time (usually samples per second) taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is specified in Hertz or samples per second.

  • SCL Clock Frequency - fSCL

    The maximum allowable clock frequency.

  • Seismic Monitoring

    Geophones (on land) or hydrophones (in sea) are used to measure reflected vibrations from the surface. There is usually a grid of these sensors that are spread over a large area. The vibrational data is recorded and analyzed to help determine subsurface characteristics that can help in identifying oil or gas reserves.

  • Sense Acceleration

    Sense Acceleration refers to the movement of an object from one point to another along a straight line or axis. It includes translational movement such as position and orientation.

    Sense Acceleration

    Discrete acceleration/ translational sensing applications call for accelerometers.

  • Sensitivity

    Sensitivity is one of the main characteristics of a microphone. Defines the output signal of a microphone per given sound pressure level, usually 94 dB SPL (1 pascal) at 1kHz. Sensitivity of analog microphones can be expressed in either mV/Pa (millivolts per pascal), or dBV. Sensitivity of digital microphones is expressed in dB FS.

  • Serial Communications

    Serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus.

  • Settling Time

    The amount of time required for an amplifier to settle to some predetermined level of accuracy or percentage of output voltage after the application of a step input.

  • Settling Time1 - ts

    The time required, following a data change, for the output to reach and remain within ±0.5 LSB of the final value.

  • Setup Time (tSU)

    The amount of time required for the digital inputs to remain static prior to a rising clock edge.

  • Shock

    Shock is a sudden force of large magnitude and short duration. Because a shock is close to an acceleration impulse, the frequency spectrum of its force can have components with high frequencies. As acceleration is proportional to the square of the frequency, a shock produces very large acceleration values.

  • Signal Chain

    A signal chain is a series of signal-conditioning electronic components that receive input (data acquired from sampling either real-time phenomena or from stored data) in tandem, with the output of one portion of the chain supplying input to the next. Signal chains are often used in signal processing applications to gather and process data or to apply system controls based on analysis of real-time phenomena. For more information about signal chains, see the Signal Chain Designer page.

  • Signal to Noise Plus Distortion (SINAD)

    The ratio of the RMS signal amplitude to the RMS value of the sum of all other spectral components including harmonics, but excluding DC.

  • Signal-to-Noise Ratio (SNR)

    The ratio of the RMS value of the measured output signal (peak or full scale) to the RMS sum of all other spectral components excluding the first 6 harmonics and DC.

  • SIL

    Every automation system must be compliant with a Safety Integrity Level (SIL) according to the IEC61508 standard. The purpose is to statistically calculate the probability of a system failing when 1) asked to perform a discrete task, and 2) continuously in operation. The SIL level denotes the probability of these events for a system. SIL level 1 is the lowest level of safety and 4 is the highest level of safety. By using a simple number scheme to represent its levels (1-4), a high-level understanding of each level is all that is required to convey SIL at management levels. This saves management from having to understand the technical aspects of SIL, while allowing them to discuss their concerns.

  • Simultaneously-Sampled Channels

    In multi-channel ADCs, simultaneous sampling is where all of the inputs on the multiple channels are captured by SHAs that are activated by the exact same clock edge.

  • Sin(X)/X

    The output of a D/A converter is a series of quantized levels that represent an analog signal whose amplitude is determined by the sin (X)/X response. At higher output frequencies, a D/A converter application may require a sin(X)/X compensation filter to normalize its output amplitude.

  • Single event burn out (SEB)

    A single-ion –induced condition that results in the destruction of the device due to the activation of a localized high current state that results in catastrophic failure.

  • Single event functional interrupt (SEFI)

    A soft error that causes the component to reset, lock-up, or otherwise malfunction in a detectable way, but does not require power cycling of the device (off and back on) to restore operability.

  • Single event gate rupture (SEGR)

    An event in which a single energetic-particle strike results in a breakdown and subsequent conducting path through the gate oxide of a MOSFET. An SEGR is manifested by an increase in gate leakage current and can result in either the degradation or the complete failure of the device.

  • Single event latch up (SEL)

    An abnormal high-current state in a device caused by the passage of a single energetic particle through sensitive regions of the device structure and resulting in the loss of device functionality.

  • Single event transient (SET)

    Voltage glitches that occur in integrated circuits (ICs) operating in a radiation environment. They are caused by ionizing particles passing through sensitive p-n junctions in the ICs. By their very nature, SETs are temporary, but they can lead to long-term effects if, for example, they corrupt instruction code in memory or trigger unwanted actions, such as power resets.

  • Single event upset (SEU)

    A single event upset (SEU) is a change of state caused by ions or electro-magnetic radiation striking a sensitive node in a micro-electronic device, such as in a microprocessor, semiconductor memory, or power transistors. The state change is a result of the free charge created by ionization in or close to an important node of a logic element (e.g. memory "bit"). The error in device output or operation caused as a result of the strike is called an SEU or a soft error.

  • Slew Rate

    The maximum rate of change of output voltage under large signal condition. The result is usually expressed in V/µ8 or volts per another unit of time.

  • Small Signal Unity Gain Frequency

    The maximum frequency at which the open-loop gain is unity or 0 dB. This applies only to signals under 200 mV. Due to slew rate limiting, it is not possible to obtain large output voltage swings at high frequencies.

  • Software Defined Radio (SDR)

    SDR is a radio architecture in which some or all of the physical layer functions are defined and performed by software in a digital processor. Functions typically accomplished in software include modulation and demodulation, filtering (including bandwidth changes), tuning, and frequency hopping. By reprogramming the software, the configuration and performance of the radio can be changed.

  • Sound Port

    The sound port is the opening in the microphone package that allows sound to enter.

  • Specialty Amplifier

    Can be built from op amps but with integrated connections and components.

  • Specialty Linear Function

    Cannot be built from simple op amps or which calculate a non-linear mathematical input.

  • Spectroscopy

    Spectroscopy is the study of the interaction between matter and radiated energy.

  • Spread Spectrum

    This communications technique has been used in secure military systems for a number of years and is now becoming popular in commercial systems. This format involves transmitting information, which has been multiplied by a pseudo-random noise (PN) sequence which essentially "spreads" it over a relatively wide frequency bandwidth. The receiver detects and uses the same PN sequence to "despread" the frequency bandwidth and decode the transmitted information. This communications technique allows greater signal density within a given transmission bandwidth and provides a high degree of signal encrytion and security in the process.

  • Spurious-Free Dynamic Range (SFDR)

    The ratio of the RMS value of the peak signal amplitude (or full-scale) to the RMS value of the amplitude of the peak spurious spectral component, which may or may not be a harmonic of the fundamental, within a specified bandwidth. SFDR is a common figure of merit for the dynamic range performance of data converters.

  • Staring Bandwidth

    The receive bandwidth of electronic warfare systems over which signals can be identified and observed. The bandwidth may be determined by a single or multiple consecutive channels receive channels and is typically considered to be the aggregate 3dB BW of the channels as presented to the digital signal processing elements of the system.

  • Stop-Band Rejection

    The amount of attenuation of a frequency outside the pass band applied to the DAC, relative to a full-scale signal applied at the DAC input within the pass band.

  • String DAC

    String DAC is a fundamental DAC architecture. Also called the Kelvin divider, an N-bit version of this DAC architecture simply consists of a string of 2N equal resistors in series dividing the Vref voltage, and 2N parallel switches configured to respectively tap the resistor string at each node. The summed output of the switches composes the DAC Vout. Digital circuitry is used to decode the DAC input word to properly control the bank of switches.

  • Supply Current

    The current required through the power supply pins to operate the amplifier with no load.

  • Synthetic-aperture Radar (SAR)

    Synthetic-aperture radar (SAR) is a form of radar whose defining characteristic is its use of relative motion, between an antenna and its target region, to provide distinctive long-term coherent-signal variations that are exploited to obtain finer spatial resolution than is possible with conventional beam-scanning means.

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