ABSTRACT
Light-emitting devices (LED) are generally separated into several groups. This chapter discusses ultraviolet, visible, near infrared, and a specialty group, vertical cavity surface-emitting laser. All the light-emitting devices can be powered using either a pulse technique or with direct current. Linear operation of a light-emitting device is dependent on many factors, including the thermal characteristics of the package, mechanical configuration of the LED chip, and ambient temperature range. The designer must reference each device data sheet for the actual characteristics of the device. The characteristics of some devices have very small linear regions and may be susceptile to temperature variations. If the device is tested in pulse mode and used in constant-current mode, the designer should take into consideration the difference in junction temperature.
