Question

Which specially fabricated pn junction diode is used for detecting light
intensity?​

Answer 1

Answer:

Let’s look at some p-n junction diodes, developed for specific applications. We will cover Zener diode and Opto-electronic junction devices including photodiodes, light emitting diode, and solar cells.

Answer 2

Explanation:

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Physics > Semiconductor Electronics: Materials, Devices and Simple Circuits > Special Purpose p-n Junction Diode

Semiconductor Electronics: Materials, Devices and Simple Circuits

Special Purpose p-n Junction Diode

Let’s look at some p-n junction diodes, developed for specific applications. We will cover Zener diode and Opto-electronic junction devices including photodiodes, light emitting diode, and solar cells.

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Questions

Zener Diode

C. Zener designed a p-n junction diode in reverse bias to operate in the breakdown region. It is used as a voltage regulator. The symbol for a Zener diode is:

diode

It is made by doping both p and n sides of the junction heavily. This leads to the formation of a very thin depletion region and an extremely high electric field across the junction even for a small reverse bias voltage (~5 V). Here is a quick look at the V-I characteristics of a Zener diode:

diode

In the above graph, you can see that as the reverse bias voltage (V) reaches the breakdown voltage of the Zener diode (Vz), there is a large change in current. Also, note that for a negligible change in the reverse bias voltage, a large change in current is produced. Hence, in a Zener diode, the voltage remains nearly constant even when there is a large change in current. This property is used to regulate supply voltages.