Electronic Engineering Glossary Terms

Channel. A carrier frequency assignment, usually with a fixed bandwidth. A connection between initiating and terminating nodes of a circuit.

Channel Capacity: The maximum possible information transfer rate through a channel, subject to specified constraints.

Channel Separation. The level of output signal of an undriven amplifier with respect to the output level of an adjacent driven amplifier. The circuit to the right shows a test set-up for Channel Separation using two operational amplifiers in a 16-pin DIP package. The Op Amps are configured as a Voltage Follower, so only one input pin is used. The signal is applied to the active channel and monitored on the quiet channel [which should have no signal].

Character. A letter, digit, or other symbol that is used as part of the organization, control, or representation of information. [ASCII Code Table]

Character Interval. In a communications system, the total number of unit intervals required to transmit any given character, including synchronizing, information, error checking, or control characters, but not including signals that are not associated with individual characters.

Characters per Second. [cps] A unit of signaling speed used to express the number of characters passing a designated point per second.

Characteristic. An inherent and measurable property of a device. Such a property may be electrical, mechanical, thermal, hydraulic, electromagnetic, or nuclear, and can be expressed as a value for stated or recognized conditions.

Characteristic Curve. An input output curve that describes the function of a component or circuit. The characteristic curve of a transistor is shown to the right, Base current by Collector current and Collector Emitter voltage.

Characteristic Impedance. [Zo] The ratio of voltage to current at any given point on a transmission line represented by a value of impedance. A measure of the electromagnetic coupling between the signal conductor and its return path. The impedance of a circuit that, when connected to the output terminals of a uniform transmission line of arbitrary length, causes the line to appear infinitely long. A uniform line terminated in its characteristic impedance will have no standing waves, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.

Charge. Represents electrical energy. A material having an excess of electrons is said to have a negative charge. A material having a shortage of electrons is said to have a positive charge.

Charge-Coupled Device. [CCD].

Charge Cycle. The period of time that a capacitor in an electrical circuit is storing a charge.

Charge Pump. A circuit that uses a capacitor to increase the output voltage of a circuit. A capacitor is charged up, either directly or indirectly, by an input signal. The capacitor voltage is than applied to or used as an output voltage. Also see IC Charge Pumps used as voltage converters.

Chassis. An equipment case. An equipment enclosure used to hold circuit boards or other components. Also refer to Styles of Equipment Enclosures.

Chassis Ground. The potential of an equipment chassis. The attached graphic shows how to connect a printed wire board [PWB] ground to chassis ground. Additional information may be found on Grounding in Chassis Design.

Circuit Ground with Chassis Ground

Chatter, Contact. In a relay, the undesired opening of mating contacts resulting from uncompensated AC operation, or external shock and vibration. The uncontrolled opening and closing of the contact of a relay. Relay Manufacturers. A discontinuity of contact closure during dwell time (exclusive of bounce time) for periods exceeding 10us.

Check Bit. A bit, such as a parity bit, derived from and appended to a bit string for later use in error detection and possibly error correction.

Check Character. A character, derived from and appended to a data item, for later use in error detection and possibly error correction.

Check-Sum. A number that has been calculated as a function of some message, by adding up the bytes in the message. The [message] data is summed with out regard overflow. Perhaps this was what early checksums were. Today, however, although more sophisticated formulae are used, the term "checksum" is still used and interchangeable with the term CRC.

Chip Inductor. A surface mount inductor. Refer to MIL-PRF-83446; Coils, Chip, Fixed or Variable, General Specification. Inductor Manufacturers

Chip Carrier. A low-profile four-sided (rectangular) part package, whose semiconductor chip cavity or mounting area is a large fraction of the package size. A package with terminals, for solid-state electronic devices, including chips which facilitates handling of the chip during assembly of the chip to other electronic elements. Also refer to an example Chip Carrier description and drawing.

Chip Enable. An input line to an integrated circuit that selects the IC. Normally found on a memory IC and used to indicate that the data on the I/O buses is meant for the IC with the active CE line.

Chip Rate. The rate of encoding. In direct-sequence-modulation spread-spectrum systems, the rate at which the information signal bits are transmitted as a pseudorandom sequence of chips.

Chirping. The rapid changing, as opposed to long-term drifting, of the frequency of an electromagnetic wave.

Choke. An inductor used to impede the flow of pulsating dc or ac by means of self-inductance. A choke is designed to have a high reactance to a particular frequency. Common-mode chokes are used to protect from EMI. High frequency chokes may be called ferrite chokes or choke baluns. RF chokes normally have air core, while low frequency chokes have ferromagnetic iron cores. [Choke Manufacturers]

Choke

Choke Joint. A joint between two sections of waveguide that provides a good electrical connection without power losses or reflections.

Chopper. An electromechanical device designed to convert direct current signals to modified square waves of the same frequency as, and bearing a definite phase relationship to, a driving sine or square wave of alternating current [diagram shown in the side-bar]. A semiconductor switch or amplifier which is turned on and off at some clock frequency.

Chopper Amplifier. A high gain low noise precision amplifier that modulates [chops] a DC signal which is then amplified by the AC chopper amplifier, the AC signal is than converted back to DC by peak detection. An OpAmp, FET or Transistor used as an AC amplifier which accepts a signal from a chopper or also serves as the chopper by going in and out of conduction [turning on and off].