Electronic Engineering Dictionary

PRBS. Refer to Pseudo Random Binary Sequence Definition.

Preamplifier. [Preamp] An amplifier that raises the output of a low-level source for further processing without appreciable degradation of the signal-to-noise ratio. A first stage amplifier that feeds a higher power amplifier. An amplifier that accepts input levels in the 10mV range.

PreAmp

Preemphasis. A system process designed to increase, within a band of frequencies, the magnitude of some (usually higher) frequencies with respect to the magnitude of other (usually lower) frequencies, in order to improve the overall signal-to-noise ratio by minimizing the adverse effects of such phenomena as attenuation differences, or saturation of recording media, in subsequent parts of the system. Example Preemphasis circuit shown to the right.

Prefetch. Saving data to a queue for later processing.

Prescaler. A circuit that generates an output that is a fraction of the input.

Preset. The input pin on a flip flop or other device that presets the output to a defined level [Q= high]. The same function as a Set pin.

Press Fit. A component that attaches to another component by friction. A press fit test point is shown to the right. A component that has a slightly larger diameter than the part it is mounting into so they lock together by friction. A Captive Screw is an example of a press-fit part.

Press Fit

Pretrigger. A trigger that occurs before a signal.

Primary Cell. An electrochemical cell in which the chemical action eats away one of the electrodes, usually the negative electrode.

Primary Winding. The winding of a transformer connected to the electrical source. Refer to Transformer Terms.

Prime Mover. The source of the turning force applied to the rotor of a generator. This may be an electric motor, a gasoline engine, a steam turbine, and so forth.

Prime Power. The primary source of electrical power to a system, and not a secondary source of power and distinct from a standby system of power. The military considers prime power as being supplied from a generator, as opposed to a commercial power source. In addition prime power is also considered to be supplied from a generator in the range of 500 to 1500kw, under 500 watts and the supply is considered to be from a tactical generator [and not prime power], perhaps a secondary power source.

Printed Circuit Assembly. A Circuit Card Assembly [CCA], a printed circuit board with the components attached.

Printed Circuit Board. [PCB] A flat, insulating surface upon which printed wiring and miniaturized components are connected in a predetermined design and attached to a common base.

Printed Circuit Board

Also refer to Printed Circuit Card Definitions. A PCB is also called Printed Wiring Board [PWB data].

Probe Coupler. A resonant conductor placed in a waveguide or cavity to insert or extract energy.

Processor. A computer or data processor component.

Product-of-Sums. A sum term or several sum terms logically multiplied together.

Product Term. A single variable product term, or the logical product of several variables.

Production Lot. A production lot shall consist of devices manufactured on the same production line(s) by means of the same production technique, materials, controls, and design.

Programmable Delay Line. A delay line with a selectable amount of delay with out the need to change taps. The example below shows a passive delay line with a fixed input and output using three control lines to change the amount of delay via a multiplexer. Related term, Delay Line. Also Delay Line vendors.

Programmable Delay Line

Programmable Logic Array. PLA. See Programmable Logic Terms and Definitions.

Programmable Logic Device. A Programmable Logic Device [PLD], or sometimes called a Programmable Logic Array [PLA] is essentially a group of uncommitted logic gates contained within an Integrated Circuit [IC]. Similar topics include; Programmable Logic Device Terms, and Programmable Logic Element Terms.
Related page, Programmable Logic Device Manufacturers.

Programmable Unijunction Transistor. [PUT] A component similar to a UJT, but requires two resistors to program particular values of the component. A 2N6028; Companies that produce a PUT.

Propagation. Waves traveling through a medium.

Propagation Delay. The amount of time for an output of an IC to change after an input was changed. Refer to IC Propagation Delay [design section of the site]. The time required for a shift in logic level to travel through one or more logic gates. Logic; The time between the specified reference points on the input and output voltage waveforms with the specified output changing from the defined level [diagram below]. The reference points on both the input and output waveforms are the same value which is midway between the maximum low-level input voltage (VIL max) and the minimum high-level input voltage (VIH min).

Propagation Time Delay. The time required for a signal to travel from one point to another.

Protective Relay. In the AC power field, a relay used to either protect equipment from a system short, overload or some other abnormal system condition, or used to limit or mitigate the damage or outage caused by the system malfunction.

Proto Board. A generic circuit board used to prototype electrical circuits. Normally the components are connected together using point-to-point wiring, either by soldering the connections or wire-wrap. An example Prototyping Board is shown to the right. Protoboards may be any shape and are available for surface mount parts having pads but not drilled holes. In some cases a portion of the board may be allocated to a preinstall circuit such as a power supply or USB interface.

Protocol. A formal set of conventions governing the format and control of interaction among communicating functional units. [Protocol Dictionary, Protocol Acronyms]. A set of specifications which define the software and hardware interface between units in the same communications system.

Protocol Data Unit. In layered systems, a unit of data that is specified in a protocol of a given layer and that consists of protocol-control information of the given layer and possibly user data of that layer.

Prototype. A pre-production, functioning specimen(s) that is the first of its type, typically used for the evaluation of design, performance, and/or production potential.

Pseudo ECL. [PECL] Emitter Coupled Logic using a power supply [Vcc] other than -5.2 volts. Also call Positive ECL when using a 5 volt power supply. Also refer to ECL Manufacturers for design data.

Pseudo Random Binary Sequence. [PRBS]. Refer to this page; PRBS Definition.

Pseudorandom Noise. Noise that satisfies one or more of the standard tests for statistical randomness.

Pseudorandom Number Generator. A device that produces a stream of unpredictable, unbiased, and usually independent bits. Also listed on the PRBS Definition page.

Pseudo-Random Pattern. A non-random pattern having a statistical properties resembling a random pattern.

Pseudo Random Sequence. [PRS]. A non-random digital sequence having a statistical properties resembling a random digital sequence.

p-type Material. A material that has an excess of hole density than electron density.