Off-line A power supply which receives its input power from the AC line, without using a 50/60 Hz power transformer prior to rectification and filtering, hence the term "off line" power supply.
Operating Range The minimum and maximum input voltage limits within which a power supply will operate to specifications. A power supply with a wide input range is recommended when the line voltage is subject to brownouts and surges.
Operating Temperature The range of ambient temperatures within which a power supply can be safely operated.
Operation Temperature The ambient temperature conditions under which the supply was designed to operate at full load. Most power supplies can operate at higher ambient if the output load is properly derated.
Optoisolator An electro-optical device which transmits a signal across a DC isolation boundary.
Output Current The maximum current which can be continuously drawn from the output of a power supply. PC motherboards and expansion cards draw 5 volt current. Drive motors draw 12 volt current.
Output Good A TTL signal which indicates that the output voltage is within its specified regulation levels. If the output goes out of regulation, the state of this signal changes.
Output Impedance The ratio of change in output voltage to change in load current.
Output Noise The AC component that may be present on the DC output of a power supply. Switch-mode power supply output noise has two components: a lower frequency component at the switching frequency of the converter and a high frequency component due to fast edges of the converter switching transitions. Noise should always be measured directly at the output terminals with a scope probe having an extremely short grounding lead.
Output Power The specified level of power of which a power supply is capable. Typically, power supplies have a continuous rating and a peak rating. These are usually a function of the ambient temperature. See "Derating."
Over Voltage Protection A power supply feature which shuts down the supply, or clamps the output, when its voltage exceeds a preset level.
Overcurrent Protection A circuit that protects the power supply and computer from excessive current, including short-circuit current.