Electronic Engineering Dictionary

Phase. The angular relationship between two alternating currents or voltages when the voltage or current is plotted as a function of time. When the two are in phase, the angle is zero; both reach their peak simultaneously. When out of phase, one will lead or lag the other; that is, at the instant when one is at its peak, the other will not be at peak value and (depending on the phase angle) may differ in polarity as well as magnitude.

Phase Angle. The number of electrical degrees of lead or lag between the voltage and current waveforms in an ac circuit. Of a periodic wave, the number of suitable units of angular measure between a point on the wave and a reference point.

Phase Coherence. The state in which two signals maintain a fixed phase relationship with each other or with a third signal that can serve as a reference for each.

Phase Delay. In the transmission of a single frequency wave from one point to another, the delay of an arbitrary point in the wave that identifies its phase.

Phase Detector. A circuit or instrument that detects the difference in phase between corresponding points on two signals.

Phase Deviation. In phase modulation, the maximum difference between the instantaneous phase angle of the modulated wave and the phase angle of the unmodulated carrier.

Phase Distortion. Distortion that occurs when the phase-frequency characteristic is not linear over the frequency range of interest. Distortion occurring in communication channels because of variations in signal propagation speeds at different frequencies.

Phase Equalization. Introducing compensation networks in a signal path to account for [reduce] the differences in the delay of various frequencies.

Phase Encoding. Data encoding that changes the width of the pulses to indicate the presence of a one or zero. A particular pulse width equates to a logic one and another width equates to a logic zero.

Phase Inverter. A circuit or component that outputs a signal that is 180 degrees out of phase with the input.

Phase Inversion. Introduction of a phase difference of 180 degrees.

Phase Jitter. Rapid, repeated phase perturbations that result in the intermittent shortening or lengthening of signal elements. Read more on Phase Jitter. A variation of signal phase about some phase reference.

Phase Lock. The process of adjusting the phase of an oscillator until it matches the phase of a reference signal.

Phase Linearity. Direct proportionality of phase shift to frequency over the frequency range of interest.

Phase-Locked Loop. [PLL] An electronic circuit that controls an oscillator so that it maintains a constant phase angle relative to a reference signal. An electronic circuit with a voltage or current-driven oscillator that is constantly adjusted to match in phase (and thus lock on) the frequency of an input signal.

Phase Margin. [PM] A safety margin of an amplifier's output signal (relative to its input) and 180 degree phase difference, as a function of frequency.

Phasemeter. An item that indicates in electrical degrees the displacement between two or more wave forms.

Phase Modulation. [PM] Angle modulation in which the phase of the carrier is controlled by the modulating waveform. The amplitude of the modulating wave determines the amount of phase shift, and the frequency of the modulation determines how often the phase shifts.

Phase Noise. The rapid short-term, random fluctuations in the phase of a wave. A measure of phase instability of a signal.

Phase Nonlinearity. Lack of direct proportionality of phase shift to frequency over the frequency range of interest.

Phase Shift. The change in phase of a periodic signal with respect to a reference. A time difference between the input and output of a signal

Phase Shifter. A device used to change the phase relationship between two ac signals. Manufacturers of RF Phase Shifters. A device used to adjust the output signal in relation to the input signal.

Phase-Shift Keying. [PSK] Similar to ON-OFF cw keying in AM systems and frequency-shift keying in FM systems. Each time a mark is received, the phase is reversed. No phase reversal takes place when a space is received. angle modulation in which the phase of the carrier is discretely varied in relation either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted.

Phase-Shift Oscillator. A circuit that oscillates by providing feedback of 180 degree phase shift of the signal back to the input. The example uses RC networks to shift the phase 60 degrees, per network and a PNP transistor as the amplifier and to shift the signal another 180 degrees to provide regenerative feedback. The value of the resistors and capacitors should be selected to provide a 60 degree phase shift at the frequency of interest.

Phase Shift Oscillator

Phase Splitter. A device that provides two output signals from a single input signal. The two output signals differ from each other in phase (usually by 180 degrees). The graphic shows a transistor phase splitter circuit configured to output to signals of equal amplitude but opposite in phase.

Phase Voltage. The greatest root mean square (effective) difference of potential between any two legs of the circuit.

Phone Jack. A wall mounted female receptacle that accepts a standard male RJ11 phone plug. Phone Plug. The removable male portion of a phone connection.

Phone Outlet

Phono Jack. [RCA Connector] An audio or video connector having two distinct circuits. Also see Audio Connector Manufacturers, normally one of which is ground and carried by the shield of a coaxial cable.

Phosphor. The material used to convert the energy of electrons into visible light.

Photocell. A light-controlled variable resistor which has a light-to-dark resistance ratio of 1:1000.

Photodarlington. An Opto Coupler that uses a darlington pair as the output stage.

Photodiode. A light-controlled PN junction. Current flow increases when the PN junction is exposed to an external light source. A semiconductor diode that produces, as a result of the absorption of photons, a photovoltage or free carriers that support the conduction of photocurrent. Photodiodes are used for the detection of optical communication signals and for the conversion of optical power to electrical power. Also Diode Manufacturers. A diode that is intended to be responsive to radiant energy.

Photodiode Coupler. An opto-coupler in which the photosensitive element is a photodiode.

Photoelectric Voltage. A voltage produced by light.

Photoemitter. A device that emits electromagnetic radiation in the visible, infrared, or ultraviolet spectral regions.

Photoetching. Chemical process of removing unwanted material in producing printed circuit boards. Also refer to PCB Terms.

Photosensitive Device. A device that is responsive to electromagnetic radiation in the visible, infrared, or ultraviolet spectral regions.

Photothyristor. A thyristor that is intended to be responsive to radiant energy for controlling its operation as a thyristor.

Photothyristor Coupler. An opto-coupler in which the photosensitive element is a photothyristor.

Phototransistor. An optoelectronic device that conducts current when exposed to light. A transistor that is intended to be responsive to radiant energy. A Phototransistor produces more current and is much more sensitive to light than the photodiode. See graphic in the side-bar.

Phototransistor Coupler. An opto-coupler in which the photosensitive element is a phototransistor.

Photovoltaic. Generating a voltage when exposed to light.

Photovoltaic Cell. [Solar Cell] A device that acts much like a battery when exposed to light and converts light energy into electrical energy.

Photovoltaic Diode. A photodiode that is intended to generate a terminal voltage in response to radiant energy.

Physical Block Address. [PBA] The PBA is the fixed, physical address of a block of data on the flash drive.

Physical Layer. Layer 1 of the OSI architectural model which defines the size and shape of the connector, the gender, and pin assignments. The physical connections to the media and their characteristics, and their interface topology. Whether the transmission is by serial bits or multiple bits in parallel, and if any Handshaking between data bits or words is required. How communication between nodes is accomplished, either by full-duplex or half-duplex transmission and the raw signaling speed and clock rate. Including the definition of symbols with respect to signal characteristics (signal amplitude and pulse time), and electrical requirements including impedance, attenuation, acceptable noise and so on.