Glossary Terms and Definitions Beginning with the Letter Q

Q See Q Factor
Q Factor A measure of the quality of a resonant (tank) circuit. A "high-Q" circuit has mostly reactive components (inductive and capacitive), with low resistance. It resonates strongly, with little damping (low loss). A high-Q circuit will have low bandwidth relative to its center frequency (that is, it will have a narrow bandwidth vs frequency curve).

Q = 2 π * (Energy stored / Energy dissipated per cycle)

Q-Injection See Charge Injection
Q-Pump See Charge Pump
Q100 See AEC-Q100
QAM Quadrature Amplitude Modulation: A modulation method in which two signals are used to amplitude-modulate two carriers that are in quadrature (90 degrees out of phase with each other). The two modulated signals are combined.

A common application is in PAL and NTSC color television transmission. Color is encoded into two analog signals (called I and Q), which modulate quadrature color carriers.

Modems also use this approach, to increase the data bandwidth they can carry (or, more accurately, to trade bandwidth for error rate or noise immunity).

QFN "Quad, flat, no-lead" package.
QFP Quad flat pack, a package type.

QPSK Symbol Constellation
Quadrature Phase Shift Keying (QPSK) is a form of Phase Shift Keying in which two bits are modulated at once, selecting one of four possible carrier phase shifts (0, 90, 180, or 270 degrees). QPSK allows the signal to carry twice as much information as ordinary PSK using the same bandwidth. QPSK is used for satellite transmission of MPEG2 video, cable modems, videoconferencing, cellular phone systems, and other forms of digital communication over an RF carrier.

See our QPSK tutorial: QPSK Modulation Demystified.

QRSS Quasi-random signal source
QS-9000 QS-9000 is the automotive quality standard surperseded by ISO/TS16949:2002 specification for component suppliers to the automotive industry.
Qs9000 See QS-9000
QSOP Quarter small-outline package
Quadrature The relation between two waves of the same frequency, but one-quarter of a cycle (90°) out of phase.
Quadrature Amplitude Modulation See QAM
Quadrature Modulation See QAM
Quadrature Phase Shift Keying See QPSK
Quadriphase Phase Shift Keying See QPSK
Quality factor See Q Factor
Quantization A process whereby the continuous range of input-signal values is divided into nonoverlapping subranges. Each of these subranges has a discrete value of the output uniquely assigned. Once a signal value falls within a given subrange, the output provides the corresponding discrete value.
Quaternary Phase Shift Keying See QPSK
QuERC Software that examines bias and transient simulation output and flags devices operating above limits. Querc is supplied by Maxim to ASIC customers.
Quiescent For an electronic circuit, a quiet state in which the circuit is driving no load and its inputs are not cycling. Most commonly used for the specification "quiescent current," the current consumed by a circuit when it in a quiescent state.