Electronic Engineering Dictionary

Ladder. A circuit structure using components connected in a chain. A filter. There are two common resistor ladder networks employed in circuit designs, an R2R Ladder and a binary weighted ladder.

Ladder Attenuator. An attenuator circuit that uses a series of components to produce known ratios of values.

Ladder Diagram. A method of showing circuit interconnection using relay contacts, used in industrial engineering. It's the same term as Ladder Logic. Refer to the ladder diagram to the right.

Ladder Filter. A type of Passive Filter.

Lag. The relative time delay between two successive events. The amount one wave is behind another in time; expressed in electrical degrees. Also refer to Phase [Angle]. The difference in time between when a circuit or system transmits a signal and when the far end receives the signal.

Lagging Current. The difference in phase between a current and the voltage that produced it.

Lagging Load. An inductive load that causes the current to lag behind the voltage in phase. A load that is primarily reactive, rather than capacitive.

Laminate. A product made by bonding two or more layers together, usually of different materials, under heat and pressure to form a single structure. The term used to describe the Fabrication of a Printed Circuit Board [PCB].

Laminated Core. A core built up from thin sheets of metal insulated from each other and used in transformers. Read more on transformer cores.

Lamp. A component that produces light, also see Manufacturers of Lamps [a number of styles].

Lamp Driver. An IC designed to supply the current required by a lamp or other device. Also refer to Manufacturers of LED and Lamp Drivers

LAN. See Local Area Network.

Lands. A metallic contact area. Conductors or runs on Printed Circuit Boards [PCB's]. However copper runs are normally called Traces, while copper pads are referred to as lands. Also refer to a separate dictionary of terms relating to Printed Wiring Board Definitions. Note the copper traces are coated so they appear green, while the copper lands have solder applied so they appear silver.

PWB Lands

Lanyard. A cord attached to a connector dust cap to insure that the cap stays attached to the connector while disconnected.

Lap Splice. [Lap Joint] A joint formed by the connecting of two or more conductors. The Lap splice is one of a number of different styles of wire splices.

Wire Lap Splice

Lap Winding. An armature winding in which opposite ends of each coil are connected to adjoining segments of the commutator so that the windings overlap.

Laser. An acronym for light amplification by stimulated emission of radiation. Laser Diode Vendors.

Latch. A circuit designed to store information. A component or circuit that maintains its assumed condition until reset by an external signal. The output of a latch will change when the clock goes high but will not latch until the clock goes low. Latches are considered bad design practice in VHDL because they are unusable in synchronous logic circuits. Refer to the schematic of a Set-Reset Latch in the right side-bar. The following are integrated circuit TTL latches; 7475, 74279, 74259, 74375, 74ALS966, a 4099 CMOS IC latch.

Latching Switch. [pulse latching], A switch that remains in a preselected position whenever the actuating voltage is removed or interrupted, and holds that preselected position until a voltage is applied to another position. A mechanical switch that remains in its present position until pushed again. Related Manufacturers;
Companies making Mechanical Switches
Companies making Semiconductor IC Switches.

Latch-Up. A unintended condition occurring in an IC by the application of an improper voltage. A circuit condition when the collector voltage of a transistor does not return to the supply voltage as the transistor is switched from saturation to cut-off, remaining in its avalanche region.

Latency. A delay. The time interval between when a device requests access to a network and when it is granted access.

Lattice Filter. A filter arranged in a bridge network.

Law of Magnetism. Like poles repel; unlike poles attract.

L Band. An out dated term used to describe a range of frequencies between 1 and 2GHz. Also see Frequency Band Usage.

LC Capacitor-Input Filter. This is the most common type of filter. It is used in a power supply where output current is low and load current is relatively constant.

LC Choke-Input Filter. This filter is used in power supplies where voltage regulation is important and where the output current is relatively high and subject to varying load conditions. Also see the section on Passive Filter Definitions. Related; Choke Manufacturers.

LC Circuit. A circuit comprising a capacitor and inductor. A tuned circuit. A Filter. A frequency dependent network used to form a resonant circuit when both the inductance reactance and capacitance reactance are equal.

Lead. The opposite of lag, as in one signal lags another by so many degrees. Also a Wire or Connection. The uninsulated part of a wire. A terminal on a component. A heavy metal with the symbol Pb.

Lead-Acid Cell. A cell in an ordinary storage battery in which electrodes are grids of lead containing an active material consisting of certain lead oxides that change in composition during charging and discharging. The electrodes or plates are immersed in an electrolyte of diluted sulfuric acid. [Battery Manufacturers].

Lead Inductance. The inductance of the I/O pins of an IC. The inductance of the lead wires connecting the internal components of an electron tube. Lead Inductance in IC pins can cause Ground Bounce.

Leading Edge. The beginning transition of a pulse from low-to-high or high-to-low.

Leadless Chip Carrier. [LCC] A type of plastic or ceramic integrated circuit package that uses terminals that are flush with the package body. Read more about the Leadless Chip Carrier Package

Lead Sheath. A continuous jacket of lead molded around a single conductor or multiple conductor cable. Generally used to ensure conductors are protected from water or extensive moisture.

Lead Wire. A short length of wire connected to a component or part and used as a lead or terminal, for that component, and used as a connection point to another part.

Leakage Current. The small amount of current that flows through the dielectric between the conductors of a transmission line. Leakage current is that current which flows through the equipment conductive paths to a solidly grounded source. A current that does not return through the intended path, but instead "leaks" to ground. A fault current.

Leakage Flux. Magnetic flux lines produced by the primary winding that do not link the turns of the secondary winding.

Leakage Resistance. The electrical resistance that opposes the flow of current through the dielectric of a capacitor. The higher the leakage resistance, the slower the capacitor discharges or leaks across the dielectric. The resistance of a reverse-biased semiconductor junction.

Least Significant Bit. [LSB].

Least Significant Digit. The digit whose position within a given number expression has the least weighting power.

LED. [Light-Emitting Diode] A semiconductor device that emits incoherent optical radiation when biased in the forward direction. Terms used with LEDs.

Left-Hand Rule for Generators. A rule or procedure used to determine the direction of current flow in a generator. Also refer to Right-Hand Rule.

Leg. A current-carrying conductor intended to deliver power to or from a load normally at an electrical potential other than ground.

Legacy. An out-of-date system or component that is still being used. Which could also be a device or component still being used after it's useful life. A legacy part may not yet be obsolete, but would not be recommended for new designs. A system or component no longer in production.

Lenz's Law. The current induced in a circuit, caused by its motion in a magnetic field or a change in its magnetic flux, in such a direction as to exert a mechanical force opposing the motion or to oppose the change in flux.

Level Translator. A circuit or component that translates an input voltage level to a different voltage level at the output. An integrated circuit that shifts or translates between two different logic levels allowing them to be interconnected as in a 10124 [TTL to ECL translator]. Also refer to How to Translate Logic Levels.

Life Cycle. The stages that a product goes through from conception to obsolescence, following a bell curve. There are six distinct phases of a Products Life Cycle:
Stage 1; Product Introduction.
Stage 2; Product Growth [rapid sales growth]
Stage 3; Product Maturity [sales grow stable, left of curve peak]
Stage 4. Product Saturation [sales begin to level out, right of peak]
Stage 5. Product Decline [Sales begin to decline, Obsolete]
Stage 6. Product Phase-Out Sales continue decline, Lifetime buys]
Products in either stage 5 or 6 are not recommended for new designs. Stage 6 is also called End-Of-Life.

Life Test. An electrical test designed to over-stress the component being tested to simulate a condition longer than the one tested for. That is a test conducted over a short period of time but is used to simulate a much longer operating condition, as in the life of the component. Another common term would be, Accelerated Stress Testing. Also refer to Unit Test Acronyms.

Light-Activated Silicon-Controlled Rectifiers. [LASCR] A pnpn which uses light to supply the gate current.

Lightbulb. The bulb used in a lamp.

Light-Emitting Diode. [LED] A PN-junction diode that emits visible light when it is forward biased. Depending on the material used to make the diode, the light may be red, green, or amber.
More on LED Terms, or LED Manufacturers.

Lighthouse Tube. An electron tube shaped like a lighthouse that is designed to handle large amounts of power at uhf frequencies.

Lightning Arrestor. A protective spark gap device for protecting different pieces of equipment such as, power poles and towers, power transformers, and circuit breakers from damage from lightning strikes by shunting the currents to ground.

Light-Pipe. A cylindrical tube or fiber used to pass light from one location to another. [Light Pipe Manufacturers].

Light-Rays. Light waves emitting from a source in straight lines.