# In this article, we are going to discuss about Diode, types of Diodes, Zener Diode & its working?

WHAT IS DIODE?

A DIODE is a device which allow flow of current in one direction, Diode have polarity, One side is positive is called anode and second side is negative is called cathode, When we see the physically diode then negative side see silver type on body marking. As per below image

Working of Diode

Diodes are working in two conditions one is forward bias and second is reverse bias.

1) FORWARD BIAS

When power supply is connected positive, (+VE) to the P type material and negative, (-VE) to the N type material across the diode which has the effect of decreasing the PN junction diodes width.

2) REVERSE BIAS

The voltage potential is connected negative, (-VE) to the P type material and the positive, (+VE) to the N-type material across the diode which has the effect of increasing the PN junction diode’s width.

Note: Diode have potential barrier for 0.7V for silicon and 0.3V for germanium, when input voltage is greater than potential barrier voltage then current will start flow.

Types of Diode:

1.        ZENER Diode

2.        P-N junction Diode

3.        Tunnel Diode

4.        Varactor Diode

5.        Schottky Diode

6.        Photo Diode

7.        PIN Diode

8.        Laser Diode

9.        Avalanche Diode

10.     Light Emitted Diode

WHAT IS ZENER DIODE?

A ZENER DIODE in which reverse voltage and reverse current can flow and block the forward voltage and current. Zener diode has two polarities same like normal diode one side is positive (Anode) & negative side (cathode) only difference is that it’s working on reverse bias and normal diode working on forward bias. When we use in circuit there is marking negative side like Z, see as per below image. It is special types of diode which use for voltage regulator.

Here we are taking example as per below circuit.

V = Terminal voltage, E = EMF, I = Current, r = Resistance

Formula – V = E – ir, E is input Voltage & V is output voltage

Suppose that

100 = 150 – 5×100

100 = 100 – 0x100

100 = 200 – 10×10

100 = 300 – 20×10

100 = 400 – 30×10

In this above example can see that input voltage is variable, resistance is fixed and current is set as per input voltage changes but output voltage is fixed.

It is use in reverse bias because it has high doping electron.

Please see below V- I characteristic of ZENER.

We can see at V-I characteristic of ZENER at one place voltage become constant & current become high in reverse bias. When current increase then automatically voltage becomes constant this is principal of ZENER.

Here is formula for this – E = dv/dr

We are taking example of 12V zener as per below circuit.

In this circuit a battery of 45V , 1K Resistance & 12 V zener which are connected in reverse bias . ‘When we apply 12 V at input side then we did didn’t get any output due one resistance is connected between them which are stable the voltage when it increase above 15V then we get 12V at zener voltage , if voltage is increase is above 40V at input side then we get only 12V at zener side this is called regulator voltage .