Dictionary of Electrical and Electronic Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

"S" to "Sec", "Sel" to "Series pa", "Series pe" to "Shr",
"Shu" to "Sil", "Sim" to "Skip", "Sky" to "Spe",
"Spi" to "Sta", "Ste" to "Stz", "Su", "Sw", "Sx" to "Sz"

Safe Operating Area. [SOA]. The area bounded under a curve such that the combination of maximum current and maximum voltage are not exceeded. Example 2N3637 Safe Operating Area Graph.

Safety Factor. The amount of a devices characteristic(s) which may be increased over and above the components normal operating rating with out causing damage to the device. In some respects a Safety Factor is the opposite of Component Derating.

Safety Margin. In electronics this is the difference between a specified value and the actual value. For example a measured value for an IC might produce a number that varies with some tolerance [10 percent], the value that gets inserted into the data sheet reflects this average value with the added safety margin of 10 percent.

Sallen-Key Filter. An active filter with a high Q and unity gain amplifier. A type of filter named for the two men that generated the equations.

Sample and Hold. A circuit that holds a sample of a signal for a short amount of time. More detail on Sample and Hold Circuits.

Sample Rate. The rate at which a signal is sampled. The frequency at which an analog signal is sampled, as in a Digital-to-Analog Converter. See D/A Converter manufacturers, graphic below.

Sampling Interval. The reciprocal of the sampling rate, i.e., the interval between corresponding points on two successive sampling pulses of the sampling signal.

Sampling Oscilloscope. An oscilloscope that samples the measured signal and reconstructs it as a visual representation. All Oscilloscopes produced for the last few decades are Sampling Scopes [Digital instead of Analog].

Sampling Rate. The rate at which a signal is sampled, see Nyquist. The number of samples taken per unit time, i.e., the rate at which signals are sampled for subsequent use, such as for modulation, coding, and quantization.

Satellite. A radio relay station that orbits the earth. A complete satellite communications system also includes earth stations that communicate with each other via the satellite. The satellite receives a signal transmitted by an originating earth station and retransmits that signal to the destination earth station(s).

Satellite Eclipse. An eclipse where the rays of the sun do not reach the satellite. This prevents recharging of the solar cells of the satellite and decreases the power to the transmitter.

Satellite-Sun Conjunction. A period when the satellite and sun are close together and the noise from the sun prevents or hampers communications.

Saturable-Core Reactor. A coil in which the reactance is controlled by changing the permeability of the core.

Saturation. The condition existing in any circuit in which an increase in the input signal produces no further change in the output. The operating point of a vacuum tube or transistor at which a further increase in grid or base current no longer produces an increase in plate or collector current. The current between the base and collector of a bipolar transistor when an increase in emitter to base voltage causes no further increase in the collector current. The point at which the output of a linear device, such as a linear amplifier, deviates significantly from being a linear function of the input when the input signal is increased. In a magnetic core, the condition in which a magnetic material has reached a maximum flux density and the permeability has decreased to a value of approximately In a communications system, the condition in which a component of the system has reached its maximum traffic handling capacity.

Saw Tooth. A waveform that appears like teeth on a saw. A Saw-Tooth waveform has a slow linear rise time and fast fall time [flyback]. Also see Periodic Waveforms.

Sawtooth Waveform

Saw Tooth Oscillator. A circuit that generates a saw-tooth waveform. A relaxation oscillator. Also refer to the Saw Tooth Oscillator Circuit topic.

S-Band. An obsolete term used to describe a band of frequencies in the microwave range. Refer to Radar Bands.

Scaling Factor. The term used to describe the use of unequal resistors in a servos summing network to compensate for differences between input and output signal levels.

Scanning. See the dictionary of Radar Terms [Electron Beam Scanning], located in a different section of this site.

Schematic. A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement. Software Schematic Tools

Transistor Schematic
Schematic Diagram

Schematic Symbol. A letter, abbreviation, or graphic design used to represent specific characteristics or components on a schematic diagram. Some organizations use different graphics to represent the same thing.

Schering Bridge. A four-arm bridge used for measuring an unknown capacitance. Refer to the schematic in the right side-bar.

Schmitt Trigger. An integrated circuit which has hystersis between an upper voltage limit and lower voltage limit and does not switch until one of those limits are reached.

Schmitt Trigger symbol

A Bistable circuit which switches based on the magnitude of the input signal and not the waveform. The output switches high when the input rises above a predetermined level and switches low when the input drops below a predetermined level.

Schottky Diode. A junction diode with the device junction formed between the semiconductor and a metal contact rather than between dissimilar semiconductor materials. Diode Manufacturers. Also called a Schottky Barrier Diode.

Schottky Diode Symbol

Schottky Transistor. A type of transistor that utilizes a combination of a transistor and a Schottky diode. The Schottky transistor shown to the right combines a Schottky diode and the transistor formed on the same silicon die [a Schottky diode used to form the transistor]. The circuit in the the right side bar shows individual Schottky diodes and individual Schottky transistors used in the same circuit, also on the same semiconductor die [an input pin to a gate].

Schottky Transistor Symbol

SCR. Refer to Silicon Controlled Rectifier. SCR Vendors.

Scratchpad Memory. A smaller faster memory section used with [slower] main memory. A memory cache.

Screen Grid. A grid placed between a control grid and the plate and usually maintained at a fixed positive potential. Used with Vacuum tubes or CRTs.

Screening. Process of applying nonconductive or semiconductive materials to a substrate to form thick film components. A process of sampling incoming or out going parts for certain parameters to insure the components are acceptable and meet their mechanical or electrical ratings.

Secondary. The output coil of a transformer. Refer to Transformer Terms.

Secondary Cell. A cell that can be recharged by a current being passed through the cell in a direction opposite to the discharge current. Battery Manufacturers

Secondary Emission. The liberation of electrons from an element, other than the cathode, as a result of being struck by other high-velocity electrons.

Secondary Loop. In a cooling system, the loop that transfers the heat from the heat source, such as electronic equipment, to the primary loop; usually distilled water.

Secondary Winding. The output winding of a transformer. The winding that receives electromagnetic induction from the primary winding. Also see Manufacturers of Transformers.

Second Detector (Demodulator). The part of the receiver that separates the audio or video component from the modulated intermediate frequency.

Sector. A predetermined, addressable angular part of a track or band on a magnetic drum or magnetic disk.

Seek Time. The time required for the access arm of a direct-access storage device to be positioned on the appropriate track. The movement of a hard disk head in search of the right data track on a platter.

PC motherboard

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