Photodiode

application

Photodiodes are also used in consumer electronics products, such as CD players, smoke detectors, and infrared remote control devices that control televisions and air conditioners. For many applications, photodiodes or other light guide materials can be used. They can all be used to measure light, often working in the camera's photometer, street lamp brightness automatic adjustment, etc. In scientific research and industry, photodiodes are often used to accurately measure light intensity because they have better linearity than other light guide materials.

structure

Photodiode is a kind of photoelectric device that generates photocurrent after being exposed to light. The structure of the photodiode is the same as that of the diode. In order to improve the stability of some photodiodes, an additional shielding ground pin is added, which looks like a phototransistor. The photodiode works under reverse bias, and its spectral response characteristics are mainly determined by the concentration of impurities doped in the semiconductor material.

Photodiodes of the same model, under certain reverse bias voltage, same intensity and different wavelengths of incident light, produce different photocurrents, but they have a maximum value. Different models of photodiodes under the same reverse bias voltage and the same intensity of incident light, the maximum value of the photocurrent generated is not the same, and the wavelength of the incident light corresponding to the maximum value of the photocurrent is also different.

working principle

When designing and manufacturing the photodiode, try to make the area of the PN junction relatively large in order to receive incident light. The photodiode works under the action of reverse voltage. When there is no light, the reverse current is extremely weak, called dark current; when there is light, the reverse current rapidly increases to dozens of microamps, called photocurrent. The greater the intensity of light, the greater the reverse current. The change of light causes the current of the photodiode to change, and the light signal can be converted into an electrical signal, which becomes a photoelectric sensor device.

When light shines on the PN junction through a skylight or a glass convex mirror, a large number of free electrons escape near the PN junction due to the absorption of the light energy address, and correspondingly the same number of holes are generated, as the free electron-hole pairs continue. As the photocurrent increases, so does the photocurrent. The photoelectric flux value is proportional to the illuminance.

The PN junction of the photodiode is arranged on the inner tomb of the transparent tube shell, and can receive light through a transparent skylight or a glass convex mirror. It adopts a reverse bias connection in the circuit.