"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"
Previous set of "P" terms and definitions
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.
Sine Wave Phase Angle
PHASE ANGLE. The number of electrical degrees of lead or lag between the voltage and current waveforms in an ac circuit.
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 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.
PHASE SHIFTER. A device used to change the phase relationship between two ac signals. Manufacturers of RF Phase Shifters
PHASE-SHIFT KEYING. 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.
| 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). |  Phase Splitter |
PHASE VOLTAGE. The greatest root mean square (effective) difference of potential between any two legs of the circuit.
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.
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) a photovoltage or (b) 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. [Diode Manufacturers]
PHOTOELECTRIC VOLTAGE. A voltage produced by light.
PHOTOETCHING. Chemical process of removing unwanted material in producing printed circuit boards. Also refer to PCB Terms.
PHOTOTRANSISTOR. An optoelectronic device that conducts current when exposed to light. Produces more current and is much more sensitive to light than the photodiode.
Photo-Transistor
PHOTOVOLTAIC CELL (SOLAR CELL). A device that acts much like a battery when exposed to light and converts light energy into electrical energy.
PHYSICAL BLOCK ADDRESS. [PBA] The PBA is the fixed, physical address of a block of data on the flash drive.
Next set of "P" Terms in the Engineering Glossary
