Zener diode


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Zener diode:

see diodediode
, two-terminal electronic device that permits current flow predominantly in only one direction. Most diodes are semiconductor devices; diode electron tubes are now used only for a few specialized applications.
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Zener diode

[′zē·nər ′dī‚ōd]
(electronics)
A semiconductor breakdown diode, usually constructed of silicon, in which reverse-voltage breakdown is based on the Zener effect.

Zener diode

A two-terminal semiconductor junction device with a very sharp voltage breakdown as reverse bias is applied. The device is used to provide a voltage reference. It is named after C. Zener, who first proposed electronic tunneling as a mechanism of electrical breakdown in insulators. See Semiconductor

A classic circuit to define a very stable current uses an operational amplifier and three stable resistors (see illustration). The voltage across the Zener itself defines a higher level from which the current is drawn. Thus, a stable noise-free Zener defines its own stable noise-free current. See Operational amplifier

The effect of temperature on the breakdown voltage can be nulled by having a second forward-biased junction, which has a small negative temperature coefficient, in series with the Zener junction. Such a device is called compensated Zener and has a breakdown voltage of 6.2 V rather than the normal 5.6 V (for the smallest possible temperature coefficient). Alternatively, a Zener junction can be part of an integrated circuit which adds a whole temperature controller to keep the silicon substrate at a constant temperature. For the very best performance, only four components are integrated into the silicon: the Zener, a heater resistor, a temperature-sensing transistor, and a current-sensing transistor. A separate selected dual operational amplifier then completes the current-and-temperature-control circuit. Such a circuit sets the chip temperature at, say 122°F (50°C), and the junction condition is then largely independent of ambient temperature. See Integrated circuits

The compact, robust Zener diode, with the circuits described to set its current and temperature, makes a fine portable voltage standard. This is used to disseminate the voltage level from national or accredited calibration laboratories to industry and to research laboratories. See Voltage measurement

References in periodicals archive ?
The value of [r.sub.d] was assumed according to [4] equal to 22 [ohm] for each Zener diode, and [R.sub.d] = [nr.sub.d], where n is the number of Zener diodes corresponding to each mode [V.sub.0].
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As shown in Figure 1, polymer-enhanced Zener diode micro-assemblies incorporate a stable Zener diode for crisp voltage clamping and a resistively nonlinear PPTC layer.
This discovery enables a very simple and cheap nanotechnology zener diode quantum gravitational wave detection technology, which will permit the study of various associated phenomena, such as solar flares, coronal mass ejections, earthquakes, eclipse effects, moon location effects, non-Poisson fluctuations in radioactivity [4], and other rate processes, and variations in radioactive decay rates related to distance of the earth from the Sun, as the 3-space fluctuations are enhanced by proximity to the sun.
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In addition to being offered in a compact, low-profile SOT23-5 package, the NCP5007 and NCP5006 incorporate built-in over-voltage protection that eliminates the need for an external zener diode. With an input voltage range of 2.7V to 5.5V, the devices are appropriate for battery power applications that use 1-cell LiIon battery or 3/4-cell NiMH batteries.
In addition to being offered in a compact, low-profile SOT23-5 package, the NCP5007 and NCP5006 incorporate builtin over-voltage protection that eliminates the need for an external zener diode. This works to simplify and miniaturize the circuit.