[Physics Class Notes] on Difference Between Diode and Rectifier Pdf for Exam

Switching diodes are also known as pulse diodes. They are used in discrete systems and act as critical devices in transmitting pulses in the forwarding direction. Rectifier diodes are redesigned to serve the purpose of rectifying alternating current. The rectifier diode is designed for rectifying alternating current. The Schottky barrier is a variant of the rectifier diode and is particularly popular in the field of digital electronics. Basically, in Switching diodes vs Rectifier diodes, the connections remain the same. It is just the applications that differ. A stable voltage drop is generated that gives a stable voltage when the current is flowing. Diodes have specialized switching operations.

 

What is a Diode?

A diode is a semiconductor device that allows an on way switch for current. It will enable the flow of current in one direction and restrict the movement in other opposite directions. Diodes are also known as rectifiers as they change the alternating form of current into direct current. Every diode has an anode and a cathode that allows current to flow only when a positive voltage is applied to the positive lead that is the anode. Every diode is forward biased when it allows current to flow. A reverse-biased diode acts as an insulator. Diodes are used as signal limiters, voltage regulators, switches, signals, and even oscillators. 

 

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What is a Rectifier?

Rectifiers are used for converting AC into DC. There are two types of rectifiers used nowadays. One of the most common rectifiers is the bridge rectifier. It supplies electric power and involves DC-DC conversion. The other different types of rectifiers are: 

• Single-phase rectifiers

• Three-phase rectifiers 

• Half-wave rectifiers 

• Full-wave rectifiers 

• Controlled rectifiers

• Uncontrolled rectifiers

• Centre tapped rectifiers

Controlled and Uncontrolled Rectifiers

Rectifiers are classified into many designs based on criteria such as power supply type, bridge layout, components used, control nature, and so on. These are primarily divided into two types: single-phase and three-phase rectifiers. Rectifiers are further categorised into three types: uncontrolled, half-controlled, and fully regulated rectifiers. Let us look at some of these rectifiers in more detail. Uncontrolled rectifiers and controlled rectifiers are the two types of rectifiers.

An uncontrolled rectifier is a rectifier whose output voltage cannot be controlled. A rectifier operates with switches, which come in both controllable and uncontrollable varieties. A two-terminal component, such as a diode, is a unidirectional device whose primary function is to enable current to flow in only one way. This device cannot be operated since it will only function if it is connected in a forward-biased configuration.

When a diode is coupled to a rectifier in any configuration, the rectifier cannot be totally controlled by an operator and is referred to as an uncontrolled rectifier. It does not allow the power to adjust depending on the load requirements. As a result, this type of rectifier is typically used in fixed or stable power supplies. This type of rectifier is made up entirely of diodes and offers a consistent output voltage depending solely on an alternating current input. 

A controlled rectifier is one in which the output voltage of a rectifier changes or varies. When we look at the defects of an uncontrolled bridge rectifier, we can see why we need a regulated rectifier. Current-controlled devices such as SCRs, IGBTs, and MOSFETs are used to convert an uncontrolled rectifier to a controlled rectifier. 

We shall have perfect control after SCRs are turned ON/OFF based on the applied gate signals. In general, these are preferable over their uncontrolled equivalents. A thyristor is another name for a silicon-controlled rectifier (SCR). It is a three-terminal diode with Anode, Cathode, and gate terminals.

Similar to a normal diode, this will perform in forwarding bias whereas, in reverse bias, it blocks current however it starts only in forward conduction once there is a signal at the input of the gate terminal. This plays an important role in output voltage control.

Types of Filters used in Rectifiers

Rectifier circuits produce a DC-like output, however, when we use a bridge rectifier, the output contains some AC components as well as DC components. To reduce the AC component, various types of filters are utilised at the rectifier’s output face. Capacitors and inductors are the most common filters used in rectifiers. 

A capacitor can be connected in parallel in a filter circuit since it allows AC and inhibits DC. At the output, any alternating current component will pass through the capacitor in the direction of the ground, resulting in a low quantity of alternating current in the output.

In a filter circuit, an inductor can be connected in series because it has inductive reactance. This reactance is an opposition to any changes, and it gives high impedance to AC and low impedance to DC because DC is a stable signal whereas AC fluctuates over time. 

An L-section filter can be used based on the configuration of a capacitor and inductor. This type of filter consists of a series-connected inductor and a parallel-connected capacitor. The Pi section filter consists mostly of two capacitors connected in parallel via an inductor connected in series.

What are the Differences Between Diode and Rectifier?

A diode is a switching device, while a rectifier is generally used for the conversion of AC voltage to DC voltage. There are some more differences between the two, such as: 

1. A diode allows the flow of current only when it is forward-biased. The diode blocks the reverse flow of current. A rectifier, on the other hand, consists of a transformer, a diode, and a filter circuit. All of these collectively convert AC to DC. 

2. In diodes, the current-carrying capacity is low, while the position in rectifiers is high. 

3. The different types of diodes are Zener diodes, photodiodes, and more. Rectifiers are of two kinds: single-phase rectifiers and three-phase rectifiers. A further division of single-phase rectifiers is full-wave rectifiers and half-wave rectifiers. 

4. Rectifiers are used in a computer system, while diodes are used in switches and clippers. 

5. Diodes were initially known as valves. They are made up of germanium or silicon most of the time.

 

Solved Examples

1. Explain forward biasing and reverse biasing? 

Forward Biasing: When the outer end of the reverse type section is connected to the ne
gative terminal, and that of the p-type section is connected to the positive terminal, the biasing of the junction is called forward bias.

The free majority charge carriers from each part move forward towards the junction. If forward bias potential is more than a potential barrier, the charges from both sections cross the intersection, and a current flows through the intersection and the circuit. It is called forward current. The size of the depletion layer decreases in forward biasing, and hence resistance decreases.

Reverse Biasing: When the outer end of the re-type section is connected to the positive terminal and that of the p-type section is connected to the negative terminal, the biasing of the junction is called reverse biasing.

The minority carrier charge is made to move toward the junction due to reverse bias. The minority carrier charge crosses the intersection, and there is minimal current order to micron across the intersection – the size of the depletion layer increases in reverse bias, and hence resistance increases.

Fun Fact About Diodes and Rectifiers

• Current flows only in one direction in a diode. 

• In 1938 the concept of the Schottky diode was first discovered. 

• Diodes are used in solar cells and also radar detectors. 

• Photodiodes and Zener diodes are beneficial electronic components. Zener diodes are used as voltage regulators. 

• All diodes are rectifiers, but all rectifiers are not diodes. 

• Every diode has a black band signifying the cathode. 

• Silicon diodes are popularly used in the market and require 0.5 volts for current to pass.

Diodes and rectifiers are important topics to learn in physics. These two topics are quite important in the chapter on electricity that students need to focus on. Understanding these two topics will enhance your conceptual foundation in this chapter and will help you score well in the exams.