Abbreviations and Acronyms

New acronyms appear in the literature each year. As time goes by, many of these acronyms fall into disuse. In a few cases, meanings may differ depending on the industry where they originate. It is possible for one abbreviation to have several meanings. When this happens, the reader must rely on the intent of the author. As an example, pH can mean hydrogen ion concentration or picohenry. The correct meaning should be obvious in context.

Authors often coin an acronym in an article when a word group is repeated many times. Sometimes, an acronym is used in one company, but it is not used by the industry. These acronyms will not appear in this list.

The following list includes the common abbreviations used in circuit board design, mathematics, electrical engineering, and physics. Fortunately, acronyms that survive rarely conflict with scientific or engineering abbreviations.

Abbreviations that do not conform to present day usage or good practice are not listed. Here are a few of the problem areas. The first letter in many engineering measurement terms is an “m”. In an abbreviation, “m” could stand for milli, micro, or mega. It is good practice to use capital M for mega, small m for milli, and the Greek μ for micro. The letter m can also stand for meter, milliwatt, and mile. In the abbreviation dBm, the m means milliwatt. If m means meter, it can usually be inferred by context.

In an old copy of “The Radio Engineers Handbook” by Terman, the term mc is used as the abbreviation for megacycle. Today, the accepted abbreviation is MHz and it is read megahertz. We have come a long way in standardizing abbreviations.

Proper names used in engineering abbreviations require a capital letter. As an example, the A in mA stands for Andre Marie Ampere the French physicist. When the word ampere is used in a sentence, it is not capitalized. “ma” is not found in this list.

This list contains most of the common abbreviations used in this book and in circuit board design. It is not a complete list. It shows how extensively we use abbreviations and acronyms. It is hard to remember them all. If you do not find an abbreviation, the internet will usually provide some help.

A	Ampere, the unit of current
ac	Alternating current. Usually a sine wave of voltage or current
A/D	Analog-to-digital
am	Amplitude modulation
amp	Ampere (not recommended)
ANSI	American National Standards Institute
ASCII	American standard code for information interchange
ASIC	Applications specific integrated circuit
ASSP	Application-specific standard product
ASTTL	Advanced Shottkey transistor–transistor logic
ATE	Automatic test equipment
B	Magnetic induction field, measured in teslas
BGA	Ball grid array
BH	B and H fields in a magnetic material. Hysteresis curves
BOM	Bill of materials
b/s	Bits per second
BST	Barium-strontium-titanate (ceramic)
BTL	Bipolar transistor logic
BTU	British thermal unit
BW	Bandwidth
c	Velocity of light
C	Capacitor, capacitance
C	Coulomb. The unit of charge
C12	A mutual capacitance
CAD	Computer-aided design
CAM	Computer-aided manufacturing
cc	Cubic centimeter
CFFT	Complex fast Fourier transform
CISPER A and B	EMI standards that are set by the EU
cm	Centimeter
CMOS	Complimentary metal oxide semiconductor
cmr	Common-mode rejection
cmrr	Common-mode rejection ratio (analog)
cos	Cosine
cot	Cotangent
CPC	Computer power center
cps	Cycles per second. Not in common use
CRT	Cathode ray tube
CSA	Canadian Standards Association
csc	Cosecant
Cu	Copper
D	Displacement field
D/A	Digital to analog
dB	Decibel. 10 log P1/P2 or 20 log V1/V2. P2 or V2 are reference levels.
dBA	Decibel-amperes
dBm	Decibel-milliwatts
dBV	Decibel-volts
dBμV	Decibel-microvolts
dc	Direct current. A steady value describing volts, current, or field strength.
Df	Dissipation factor
DFF	D flip flop
DFM	Design for manufacturability
DFT	1. Design for test 2. Discrete Fourier transform
DIP	Dual inline package
Dk	Dielectric constant
DRAM	Dynamic random access memory
DTL	Decoupling transmission line
e	2.71828. Base of natural logarithms
E	Electric field strength. Basic unit is volts per meter
E	Energy in joules
ECAD	Electronic computer-aided design
ECL	Emitter-coupled logic
EDA	Electronic design automation
EE	Electrical engineer
EIA	Electronics Industry Association
EM	Electromagnetic
EMC	Electromagnetic compatibility
emf	Electromotive force, voltage
emi	Electromagnetic interference
ENIG	Electroless nickel/immersion gold
EPROM	Electrically programmable read only memory
ESD	Electrostatic discharge
ESL	Equivalent series inductance
ESR	Equivalent series resistance
EU	European Union
f	Frequency
F	Farad, the unit of capacitance
FB	Feedback
FCC	Federal Communications Commission
FET	Field effect transistor
FFT	Fast Fourier transforms
FIFO	First in first out
FILO	First in last out
fm	Frequency modulation
FP	Field programmable
FPGA	Field programmable gate array
FR-4	Flame resistant class 4 circuit board laminate. Glass epoxy
FTTL	Fast TTL
g	Gram
G	Gauss, 10−4 teslas
GaAs	Gallium arsenide
Gb/s	Gigabits per second
GHz	Gigahertz, 109 Hz
GND	Ground
GTL	Gunning transistor logic
H	1. Magnetic field strength, Basic unit is amperes per meter 2. henry, unit of inductance
HASL	Hot air solder leveling
HDI	High density interconnect
HF	High frequency
HSTL	High speed transceiver logic
Hz	hertz (frequency). 1 Hz = 1 cycle per second
IBIS	I/O buffer information specification
i	1. Varying current. 2. Square root of −1
IC	Integrated circuit
id	Inside diameter
IEEE	Institute of Electrical and Electronic Engineers
I/O	Input/output
IP	Intellectual property
IPC	Institute of Printed Circuits
IR	Infrared
ISDN	Integrated Services Digital Network
J	Joule
JEDEC	Joint Electronics Device Engineering Council
JFET	Junction FET
k	Kilo, 103
kb/s	Kilobytes per second
KB	Keyboard
kg	Kilogram
kHz	Kilohertz, 103 Hz
km	Kilometer, 103 m
kV	Kilovolt, 103 V
kW	Kilowatt, 103 W
kΩ	Kiloohms, 103 ohm
L	Inductor, inductance
L12	Mutual inductance
LAN	Local area network
LED	Light emitting diode
LCC	Leaded chip carrier
LICA	Low inductance capacitor array
ln	Natural logarithm (base e)
log	Logarithm (base 10)
LRC	Inductor/resistor/capacitor
LVCMOS	Low voltage CMOS
LVDS	Low voltage differential signaling
m	1. Meter 2. Milli
M	Mega, 106 (M mean 1000 in Roman numerals but not in engineering)
mA	Milliampere, 10−3 A
Mb/s	Mega bits per second
MCAD	Mechanical computer-aided design
MCM	Multi chip module
mH	Millihenry
MHz	Megahertz, 106 Hz
mil	0.001 inches
Mil	Military
Mil Std	Military standard
mJ	Millijoule
mm	Millimeter
mmf	Magneto motive force
MOS	Metal oxide semiconductor
MOSFET	Metal oxide semiconductor field effect transistor
ms or msec	Millisecond, 10−3 s
mV	Millivolt, 10−3 V
mW	Milliwatt, 10−3 W
mΩ	Milliohm, 10−3 ohm
MΩ	Megaohm, 106 ohm
N	Newton
n	Nano, 10−9
nA	Nanoampere, 10−9 A
NEC	National Electrical Code
NEMA	National Electrical Manufacturing Association
nF	Nanofarad, 1000 pF, 0.001 μF, 10−9 F
nH	Nanohenry
nm	Nanometer
npn	Transistor made from a p-doped semiconductor layer between two n layers
ns	Nanosecond, 10−9 s
OC	Optical carrier
od	Outside diameter
OEM	Original equipment manufacturer
p	Pico, 10−12
PC, pc	1. Printed circuit 2. Personal computer
PCA	Printed circuit assembly
PCB	Printed circuit board
PCI	Personal computer interface
PE	Professional engineer
PECL	Positive ECL
pf	Power factor
pF	Picofarad, 10−12 F
pH	Picohenry, 10−12 H
PLL	Phase-locked loop
pn	Junction of positive and negative doped semiconductor, diode
pnp	Transistor, n-doped semiconductor between two p layers
ps	Picosecond, 10−12 s
PTFE	Polytetrafluoroethylene (dielectric)
PWB	Printed wiring board
PWR	Power
Q	A measure of losses in resonance. Low loss equals high Q
QA	Quality assurance
QFP	Quad flat pack
R	Resistor, resistance
RAM	Random access memory
RC	Resistor/capacitor
rf	Radio frequency
rfi	Radio frequency interference, general interference
rms	Root mean square
RoHM	Reduction of hazardous material (lead free)
ROM	Read only memory
rpm	Revolutions per minute
rps	Revolutions per second
RTI	Referred to input
RTO	Referred to output
s	Second
SCR	Silicon controlled rectifier
sec	1. Second (not recommended) 2. Secant
Si	Silicon
SI	Signal integrity
SIP	Single inline package
SMD	Surface mounted device
SMT	Surface mount transistor
SPICE	Special program for integrated circuit emulation
SRAM	Static random access memory
SWR	Standing wave ratio
t	Time
T	1. tesla, the unit of magnetic induction 2. Temperature
tan	Tangent
TBD	To be determined
TC	Temperature coefficient
TDR	Time domain reflectometer
TE	Transverse electric (wave)
TEL	1. Transitional electrical length. The distance a wave travels in a rise time 2. Telephone
TELCO	Telephone company
TT	Resin transition temperature in laminates
TIA	Telecommunications Industry Association
TL	Transmission line
TM	Transverse magnetic (wave)
TQFP	Thin quad flat pack
TTL	Transistor–transistor logic
TV	Television
UHF	Ultrahigh frequency
UL	Underwriters Laboratories
USB	Universal serial bus
UTP	Unshielded twisted pair
v	Varying voltage
V	Volt
V	Volume usually in meters cubed
VA	Volt-amperes
VAR	Volt amperes reactive
Vcc	Positive voltage on a circuit board
VCR	Voltage controlled rectifier
Vdd	Positive voltage on a circuit board
VME	Type of bus and hardware protocol
VOHmax	Highest loaded voltage for a logic 1 of a driver
VOHmin	Lowest loaded voltage for a logic 1 of a driver
VOLmax	Highest loaded voltage for a logic 0 of a driver
Vss	The ground or most negative voltage on a circuit board
VSW	Voltage standing wave
W	Watt
W	Work
wan	Wide area network
X	Reactance in ohms
Y	Admittance in mhos
Z	Impedance in ohms
β	Current gain for a transistor
ε R	Relative dielectric constant, permittivity
θ	Angle, phase, or phase angle
λ	Wavelength
μR	Relative permeability
μ	Micro, 10−6
μA	Microampere, 10−6 A
μF	Microfarad, 10−6 F
μH	Microhenry
μm	Micrometer, 10−6 m
μs	Microsecond, 10−6 s
μV	Microvolt, 10−6 V
π	3.14159
ρ	1. Resistivity 2. Reflection coefficient
σ	Conductivity
τ	Transmission coefficient
τr	Rise or fall time
ϕ	Angle, phase, or phase angle
ω	Radian frequency, 2πf
Ω	ohm