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octave
Interval between two sounds whose fundamental frequencies differ by a ratio of 2 to 1. 440 Hz. is one octave above 220 Hz.
offset null
An op amp control pin used to eliminate the effects of internal component voltages on the output of the device.
ohm
Unit of resistance symbolized by the Greek capital letter omega (W).
ohmmeter
Device used to measure electrical resistance.
Ohm’s law
Relationship between voltage, current and resistance. Ohm’s law states that current in a resistance varies in direct proportion to voltage applied and inversely proportional to resistance.
Ohms per volt
Refers to a value of ohms per volt of full scale defection for a moving coil meter movement. The number of ohms per volt is the reciprocal of the amount of current required to produce full scale deflection of the needle. A meter requiring 50 microamps for full scale deflection has an internal resistance of 20 kW per volt. The higher the ohms per volt rating, the more sensitive the meter.
one-shot
Monostable multivibrator.
op-amp
Abbreviation for operational amplifier.
operational amplifier
A high gain DC amplifier that has a high input impedance and a low output impedance. Op-amps are the most basic type of linear integrated circuits.
oscillate
To produce a continuous output waveform without an input signal present.
oscillator
An electronic circuit that produces a continuous output waveform with only DC applied.
oscilloscope
An instrument used to display a signal graphically. Shows signal amplitude, period and waveshape in addition to any DC voltage present. A multiple trace oscilloscope can show two or more waveforms at the same time for phase comparison and timing measurements.
out of phase
When the maximum and minimum points of two or more waveshapes do not occur at the same time.
output
Terminal at which a component, circuit or piece of equipment delivers current, voltage or power.
output impedance
Impedance measured across the output terminals of a device without a load connected.
output power
Amount of power a component, circuit or system can deliver to a load.
overload
Condition that occurs when the load is greater than the system was designed to handle. (Load resistance too small, load current too high.) Overload results in waveform distortion and/or overheating.
overload protection
Protective device such as a fuse or circuit breaker that automatically disconnects a load when current exceeds a predetermined value.
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P
paper capacitor
Fixed capacitor using oiled or waxed paper as a dielectric.
parallel
Circuit having two or more paths for current flow. Also called shunt.
parallel resonant circuit
Circuit having an inductor and a capacitor in parallel with one another. Circuit offers a high impedance at resonant frequency. Sometimes called a "tank circuit."
pass band
The range of frequencies that will be passed and amplified by a tuned amplifier. Also the range of frequencies passed by a band pass filter.
passive component
Component that does not amplify a signal. Resistors and capacitors are examples.
passive filter
A filter that contains only passive or non amplifying components.
passive system
System that emits no energy. It only receives. It does not transmit or reveal its position.
peak
Maximum or highest amplitude level.
peak inverse voltage
(PIV) The maximum rated value of a AC voltage acting in the direction opposite to that in which a device is designed to pass current.
peak to peak
Difference between the maximum positive and maximum negative values of an AC waveform.
pentavalent element
Element whose atoms have five valence electrons. Used in doping intrinsic silicon or germanium to produce n-type semiconductor material. Most commonly used pentavalent materials are arsenic and phosphorus.
percent of regulation
The change in output voltage that occurs between no-load and full-load in a DC voltage source. Dividing this change by the full-load value and multiplying the result by 100 gives percent regulation.
percent of ripple
The ratio of the effective rms value of ripple voltage to the average value of the total voltage. Expressed as a percentage.
period
Time to complete one full cycle of a periodic or repeating waveform.
permanence
Magnetic equivalent of magnetic inductance and consequently equal to the reciprocal of reluctance, just as conductance is equal to the reciprocal of resistance.
permanent magnet
Magnet normally made of hardened steel that retains its magnetism indefinitely.
permeability
Measure of how m how much better a material is as a path for magnetic lines of force with respect to air which has a permeability of one. Symbolized by the Greek lower case letter mu (m).
phase
Angular relationship between two waves.
phase angle
Phase difference between two or more waves, normally expressed in degrees.
phase shift
Change in phase of a wave form between two points, expressed as degrees of lead or lag.
phase splitter
Circuit that takes a single input signal and produces two output signals that are 180° apart in phase.
phonograph
Piece of equipment used to reproduce sound stored on a disk called a phonograph record.
phosphor
Luminescent material applied to the inner face of a cathode ray tube that when bombarded with electrons will emit light of various colors.
photoconductive cell
Material whose resistance decreases or conductance increases when exposed to light.
photoconduction
A process by which the conductance of a material is change by incident electromagnetic radiation in the visible light spectrum.
photodetector
Component used to detect or sense light.
photodiode
A semiconductor diode that changes its electrical characteristics in response to illumination.
photometer
Meter used to measure light intensity.
photon
Discrete portion of electromagnetic energy. A small packet of light.
photovoltaic cell
Component commonly called a solar cell used to convert light energy into electrical energy.
pi
Value representing the ratio between the circumference and diameter of a circle and equal to approximately 3.142.
piezoelectric crystal
Crystal material that will generate a voltage when mechanical pressure is applied and conversely will undergo mechanical stress when subjected to a voltage.
piezoelectric effect
The production of a voltage between opposite sides of a piezoelectric crystal as a result of pressure or twisting. Also the reverse effect which the application of a voltage to opposite sides causes a deformation to occur at the frequency of the applied voltage. (Converts mechanical energy into electrical energy and electrical energy into mechanical energy.)
pinch-off region
A region on the characteristic curve of a FET in which the gate bias causes the depletion region to extend completely across the channel.
plastic film capacitor
Capacitor in which alternate layers of aluminum foil are separated by thin films of plastic dialectric.
plate
Conductive electrode in either a capacitor or battery. In vacuum tube technology, it is the name given to the anode.
plug
Movable connector that is normally connected into a socket or jack.
pnp transistor
A bipolar junction transistor with an n-type base and p-type emitter and collector.
pole
In an active filter, a single RC circuit. A one pole filter has one capacitor and one resistor. A two pole filter has two RC circuits and so on.
polar coordinates
Either of two numbers that locate a point in a plane by its distance from a fixed point and the angle this line makes with a fixed line.
polarity
Term used to describe positive and negative charges.
polarized
A component which must be connected in correct polarity to function and/or d/or prevent destruction. Example: Electrolytic capacitor.
positive
Polarity of point that attracts electrons as opposed to negative which supplies electrons.
positive ground
A system whereby the positive terminal of the source is connected to the system’s conducting chassis.
positive ion
Atom that has lost one or more valence electrons resulting in a net positive charge.
potential difference
Voltage difference between two points which will cause current to flow in a closed circuit.
potential energy
Energy that has potential to do work because of its position relative to others.
potentiometer
A variable resistor with three terhree terminals. Mechanical turning of a shaft can be used to produce variable resistance and potential. Example: A volume control is usually a potentiometer.
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