Diodes, Transistors & Binary Systems: Electronics Essentials

Posted on Mar 3, 2025 in Technology

Diodes: The Basics

A diode is a two-terminal electronic component that allows current to flow in one direction only. It is formed by a p-n junction, where p-type and n-type semiconductors are joined together.

• When a forward bias is applied to the diode (positive terminal to p-type and negative terminal to n-type), the junction barrier is reduced, allowing current to flow.
• When a reverse bias is applied (positive terminal to n-type and negative terminal to p-type), the junction barrier is increased, preventing current flow.
• Diodes are commonly used in various applications, including rectification (converting AC to DC), switching, signal detection, and voltage regulation.

P-Type and N-Type Semiconductors

• P-type semiconductor: A semiconductor material that has an excess of holes (electron vacancies). These holes can act as positive charge carriers.
• N-type semiconductor: A semiconductor material that has an excess of electrons. These electrons can act as negative charge carriers.
• The doping process, which involves adding impurities to a pure semiconductor material, creates p-type and n-type semiconductors.

Diode Applications

• Rectification: Converting AC voltage to DC voltage using diodes in circuits like half-wave and full-wave rectifiers.
• Switching: Controlling the flow of current in circuits using diodes as switches.
• Signal detection: Detecting and recovering information from modulated signals using diodes in demodulators.
• Voltage regulation: Maintaining a constant voltage level using diodes in Zener diode voltage regulators.
• Light-emitting diodes (LEDs): Converting electrical energy into light energy.
• Photodiodes: Converting light energy into electrical energy.

Bipolar Junction Transistor (BJT)

A BJT is a three-terminal semiconductor device that amplifies or switches electrical signals. It consists of three regions: emitter, base, and collector. The emitter-base junction is forward biased, allowing current to flow from the emitter to the base. The base-collector junction is reverse biased, creating a small collector current. The transistor’s amplification property is due to the relationship between the base current and the collector current.

Here’s a basic diagram of an NPN BJT:

Input/Output Characteristics: Common Base NPN

• Input characteristics: A plot of base current (IB) versus emitter-base voltage (VBE) for a fixed collector-emitter voltage (VCE).
• Output characteristics: A plot of collector current (IC) versus collector-emitter voltage (VCE) for different values of base current (IB).

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Binary System Explained

The Binary System uses base 2 (two digits: 0 and 1). Each digit is called a bit and represents numbers using a combination of 0s and 1s.

Decimal System

The Decimal System uses base 10 (ten digits: 0 to 9) and represents numbers using a combination of digits from 0 to 9. For example, the decimal number 10 is equivalent to the binary number 1010.