{{no footnotes, date=September 2013
A QUADRAC is a special type of '' thyristor'' which combines a DIAC and a TRIAC in a single package. The DIAC is the triggering device for the TRIAC. Thyristors are four-layer (PNPN) semiconductor devices that act as switches,
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an Power ...
s or voltage regulators in a variety of applications. When triggered, thyristors turn on and become low-resistance current paths. They remain so even after the trigger is removed, and until the current is reduced to a certain level (or until they are triggered off). Diacs are bi-directional
diode
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.
A diode ...
s that switch ACvoltages and trigger triacs or silicon-controlled rectifiers (SCRs). Except for a small leakage current, diacs do not conduct until the breakover voltage is reached. Triacs are three-terminal, silicon devices that function as two SCRs configured in an inverse, parallel arrangement. They provide load current during both halves of the AC supply voltage. By combining the functions of diacs and triacs, QUADRACs eliminate the need to buy and assemble discrete parts.
QUADRACs are used in lighting control, speed control, and temperature modulation control applications. They carry performance specifications such as peak repetitive off voltage, peak repetitive reverse voltage,
root mean square
In mathematics and its applications, the root mean square of a set of numbers x_i (abbreviated as RMS, or rms and denoted in formulas as either x_\mathrm or \mathrm_x) is defined as the square root of the mean square (the arithmetic mean of the ...
(RMS) on-state current, and temperature junction. Peak repetitive off voltage is the maximum, instantaneous value of the off-state voltage that occurs across a thyristor, including all repetitive transient voltages and excluding all non-transient voltages. Peak repetitive reverse voltage is the maximum peak reverse voltage that may be applied continuously to the main terminals (anode and cathode) of QUADRACs. RMS on-state current is the maximum RMS current allowed for the specified use-case temperature. Temperature junction for QUADRACs is expressed as a full-required range.
Packages
QUADRACs are available in a variety of
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
(IC) package types with different numbers of pins. Basic IC packages types for QUADRACs include discrete packaging (DPAK), power packaging (PPAK), and in-line packaging (IPAK). Other IC package types include diode outline (DO), transistor outline (TO), and small outline transistor (SOT). QUADRACs that use metal electrode leadless face (MELF) packaging have metallized terminals at each end of a cylindrical body. Other available package types for QUADRACs include thin small outline package (TSOP), thin shrink small outline L-leaded package (TSSOP), and thin small outline J-lead (TSOJ) package.