Glossary Terms and Definitions Beginning with the Letter O

OC Overcurrent
OC-48 A fiber-optic line capable of 2400 megabits per second.
OEM Original equipment manufacturer
OFC Open fiber control
OFDM Orthogonal Frequency Division Multiplexing: A method for multiplexing signals which divides the available bandwidth into a series of frequencies known as tones. Flarion uses the 5GHz channel and divides each channel into 400 discrete tones (each at slightly different frequency). Orthogonal tones do not interfere with each other when the peak of one tone corresponds with the null. All frequencies fade but the rapid switching, frequency-hopping technique is intended to allow more robust data service.
ohm See Impedance
OLED Organic Light-Emitting Diode: An LED made with organic materials. The diodes in displays made with OLEDs emit light when a voltage is applied to them. The pixel diodes are selectively turned on or off to form images on the screen. This kind of display can be brighter and more efficient than current LCD displays.
OLT Optical line transmission
One Wire See 1-Wire
OneWire See 1-Wire
ONU ONT (Optical Network Termination), also called ONU (Optical Network Unit), refer to the consumer end equipment in an optical Fiber to the Home (FTTH) link. The ONT/ONU receives downstream data from the OLT (Optical Line Termination) through the passive optical splitters and provides video, voice, and broadband services to the consumer.
Op amp Operational amplifier: The ideal op amp is an amplifier with infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. It has positive and negative inputs which allow circuits that use feedback to achieve a wide range of functions.

Using op amps, it's easy to make amplifiers, comparators, log amps, filters, oscillators, data converters, level translators, references, and more. Mathematical functions like addition, subtraction, multiplication, and integration can be easily accomplished.

Practical, real-world op amps have finite characteristics but in most applications, are close enough to the ideal to make a huge range of inexpensive, high-performance analog applications possible. They are the building block for analog design.

One key to op amp design is nodal analysis. Since the input impedance is infinite, the current in and out of the + and - input nodes defines the circuit's behavior.

See: Nodal Analysis of Op Amp Circuits for a good tutorial on this topic.

Also see other amplifier tutorials at: Amplifier Tutorials.

Maxim has hundreds of op amps (and other amplifiers).

opamp See Op amp
Open-collector See Open-drain
Open-drain An open-drain or open-collector output pin is driven by a single transistor, which pulls the pin to only one voltage (generally, to ground). When the output device is off, the pin is left floating (open, or hi-z). A common example is an n-channel transistor which pulls the signal to ground when the transistor is on or leaves it open when the transistor is off.

Open-drain refers to such a circuit implemented in FET technologies because the transistor's drain terminal is connected to the output; open-collector means a bipolar transistor's collector is performing the function.

When the transistor is off, the signal can be driven by another device or it can be pulled up or down by a resistor. The resistor prevents an undefined, floating state. (See the related term, hi-z.)

operational amplifier See Op amp
operational transconductance amplifier See Transconductance Amplifier
Optical Network Termination See ONU
Optical Network Unit See ONU
OR Combining two signals so that the output is on if either signal is present. This can be accomplished by an OR logic gate (two inputs, one output which is high if either input is).

It can also be done with a "wired-OR" connection in which two signals are simply wired together and either one of them can raise the level. This works when the signals are driven by a source that only pulls up or only pulls down, with a resistive load (e.g. an "open collector" output).

OR-ing See OR
Orthogonal Frequency Division Multiplexing See OFDM
OTA See Transconductance Amplifier
Output to Input Ratio The ratio between the sensed current and the output current of the amplifier.
Overvoltage Protection Overvoltage Protector (OVP) refers to a circuit that protects downstream circuitry from damage due to excessive voltage. An OVP monitors the DC voltage coming from an external power source, such as an off-line power supply or a battery, and protects the rest of the connected circuitry using one of two methods: a crowbar clamp circuit or a series-connected switch.

The crowbar short-circuits or clamps the supply line to limit the voltage, possibly triggering other forms of protection such as a fuse. See Crowbar.

The series-connected switch uses a MOSFET or transistor connected as a switch in series with the supply line. During an overvoltage condition, the OVP circuit rapidly shuts off the MOSFET and disconnects the downstream circuit.

See: Protection and Isolation products.

OVP See Overvoltage Protection