how many type of diode?
Answers
Answer:
The following are the characteristics of the diode: Forward-biased diode.Reverse-biased diode. Zero biased diode.
1. P-N Junction Diode
A P-N junction is a semiconductor device, which is formed by P-type and N-type semiconductor material. P-type has a high concentration of holes and N-type has a high concentration of electrons. Holes diffusion is from p-type to n-type and electron diffusion is from n-type to p-type.
The donor ions in the n-type region become positively charged as the free electrons move from the n-type to p-type. Hence, a positive charge is built on the N-side of the junction. The free electrons across the junction are the negative acceptor ions by filling in the holes, then the negative charge established on the p-side of the junction is shown in the figure.
An electric field formed by the positive ions in the n-type region and negative ions in p-type regions. This region is called the diffusion region. Since the electric field quickly sweeps free carriers out, hence the region is depleted of free carriers. A built-in potential Vbi due to Ê is formed at the junction is shown in the figure.
Functional Diagram of P-N Junction Diode:
Functional Diagram of P-N Junction Diode
Functional Diagram of P-N Junction Diode
Forward Characteristics of P-N Junction:
When the positive terminal of the battery is connected to P-type and the negative terminal is connected to N-type is called forward bias of P-N junction is shown figure below.
Forward Characteristics of P-N Junction
Forward Characteristics of P-N Junction
If this external voltage becomes greater than the value of the potential barrier, approximately 0.7 volts for silicon and 0.3V for Ge, the potential barrier is crossed and the current starts flowing due to movement of electrons across the junction and same for the holes.
P-N Junction Forward Bias Characteristics
P-N Junction Forward Bias Characteristics
Reverse Characteristics of P-N Junction:
When a positive voltage is given to the n-part and negative voltage to the p-part of the diode, it is said to be in reverse bias condition.
P-N Junction Reverse Characteristics Circuit
P-N Junction Reverse Characteristics Circuit
When a positive voltage is given to N-part of the diode, the electrons move towards the positive electrode and the application of negative voltage to the p-part makes the holes move towards the negative electrode. As a result, the electrons cross the junction to combine with the holes in the opposite side of the junction and vice versa. As a result, a depletion layer is formed, having a high impedance path with a high potential barrier.
P-N Junction Reverse Bias Characteristics
P-N Junction Reverse Bias Characteristics
Applications of P-N Junction Diode:
P-N junction diode is a two-terminal polarity sensitive device, the diode conducts when in forwarding bias and diode not conducts when reverse bias. Due to these characteristics, P-N junction diode is used in many applications like
Rectifiers in DC power supply
Demodulation circuits
Clipping and clamping networks
2. Photodiode
The photodiode is a kind of diode which generates current proportional to the incident light energy. It is a light to voltage/current converter that finds applications in security systems, conveyors, automatic switching systems, etc. The photodiode is similar to an LED in construction but its p-n junction is highly sensitive to light. The p-n junction may be exposed or packaged with a window to enter light into the P-N junction. Under the forward biased state, current passes from the anode to cathode, while in the reverse-biased state, photocurrent flows in the reverse direction. In most cases, the packaging of Photodiode is similar to LED with anode and cathode leads projecting out from the case.
Photo Diode
Photo Diode
There are two kinds of Photodiodes – PN and PIN photodiodes. The difference is in their performance. The PIN photodiode has an intrinsic layer, so it must be reverse biased. As a result of reverse biasing, the width of the depletion region increases, and the capacitance of the p-n junction decreases. This allows the generation of more electrons and holes in the depletion region. But one disadvantage of reverse biasing is that it generates noise current that may reduce the S/N ratio. So reverse biasing is suitable only in applications that require higher bandwidth. The PN photodiode is ideal for lower light applications because the operation is unbiased.
PhotodiodeThe photodiode works in two modes namely Photovoltaic mode and Photoconductive mode. In the photovoltaic mode (also called Zero bias mode), the photocurrent from the device is restricted and a voltage builds up. The photodiode is now in the Forward biased state and a “Dark current” starts flowing across the p-n junction. This flow of dark current occurs opposite to the direction of the photocurrent. The dark current generates in the absence of light. The dark current is the photocurrent induced by the background radiation plus the saturation current in the device.