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Electronics Dictionary - O

 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. open loop gain Gain of an amplifier when no feedback is present. open loop mode An amplifier circuit having no means of comparing the output with the input. (No feedback.) 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 waveshpes 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 Codition 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 outomatically disconnects a load when current exceeds a predetermined value.
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