Here’s Everything You Need To Know About Transistors

What Is A Transistor?

A transistor is a tiny but powerful electronic component that acts like a switch or an amplifier. It is made from a semiconductor material, usually silicon, and has three legs for connection to circuits. By applying a small voltage or current to one leg, you can control the flow of a much larger current through the other two legs.

The concept of a transistor is nearly a century old; physicist Julius Lilienfeld proposed the field-effect transistor (FET) in 1926. In 1947, the device was finally invented by physicists John Bardeen, Walter Brattain and William Shockley at Bell Labs. Bell Labs was also the crucible where the most widely used transistor, the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), was invented by Mohamed Atalla and Dawon Kahng in 1959.

The transistor has since become one of humanity’s most important inventions, on par with the wheel and written language. MOSFETs are the most numerously produced artificial objects in history, with more than 13 sextillion (13,000,000,000,000,000,000,000!) manufactured by 2018. 

For an idea of how large that number is, consider the Apple A17, the CPU in iPhone 15 and its iterations, which contains 19 Bn transistors. To match the number of transistors made till 2018, Apple would have to manufacture more than 684 Bn units of iPhone 15. Considering that it takes 1 day for an iPhone to go from parts to a finished product, it would take 1.9 Bn years of nonstop manufacturing.

How Do Transistors Work?

Transistors are like microscopic valves that control electricity. They use a small electrical current to regulate a much larger current, acting as both switches and amplifiers. Here is a simplified explanation of how they work:

• Basic Structure: A transistor is made of a semiconductor material, typically silicon. It has three terminals – emitter, base, and collector.
• Control Mechanism: The base acts like a control gate. Applying a small voltage or current to the base affects the flow of electricity between the emitter and collector.
• Switching Operation: With no voltage on the base, the transistor acts like a closed switch, blocking current flow from emitter to collector. Applying a voltage to the base opens the switch, allowing current to flow freely from emitter to collector.
• Amplification Operation: A small change in voltage at the base can significantly alter the current flow between emitter and collector. This is like using a small force to control a much larger object.

What Are The Two Types Of Transistors?

There are two main types of transistors:

• Bipolar Junction Transistor (BJT): Uses both positive and negative charges (electrons and holes) for operation. BJTs are further classified into NPN (negative-positive-negative) and PNP (positive-negative-positive) transistors based on their structure and operation.
• Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET): Primarily uses electric fields to control current flow. It is the most common type of transistor in integrated circuits today due to smaller size and lower power consumption.

What Makes Transistors So Crucial For Modern Electronics?

Transistors are fundamental to modern electronics for several reasons:

• Miniaturisation: Transistors are significantly smaller than their predecessors, vacuum tubes. This miniaturisation enabled the development of smaller, more portable electronic devices.
• Efficiency: Transistors use less power than vacuum tubes, leading to more energy-efficient electronics. This is crucial for battery-powered devices like smartphones and laptops.
• Scalability: Transistors can be mass-produced very efficiently, allowing for the creation of complex integrated circuits containing billions of transistors. This has fuelled the exponential growth of computing power.
• Versatility: Transistors can function as both switches and amplifiers, making them highly versatile building blocks for electronic circuits.

Chip Design, Transistors & Moore’s Law

Transistors, the microscopic building blocks of electronics, are intricately linked to chip design and Moore’s Law in their journey towards miniaturisation and driving modern electronics. 

Transistors act as electronic switches and amplifiers, and by strategically placing them on a chip, chip designers create complex circuits that power our devices. Moore’s Law, the observation that the number of transistors on a chip doubles roughly every two years, has fuelled the demand for ever-smaller transistors. 

This miniaturisation necessitates advancements in chip design to accommodate these tiny components. This continuous miniaturisation of transistors, driven by Moore’s Law, has been a defining force in the incredible progress of modern electronics.

What Is The Future Of Transistors?

The future of transistors is being actively explored as miniaturisation according to Moore’s Law faces limitations. Here are some potential areas of focus:

• New Materials: Exploring alternative materials beyond silicon to create transistors that can operate more efficiently at smaller sizes. Materials like gallium nitride (GaN) and carbon nanotubes are being investigated for their potential.
• New Transistor Structures: Developing new transistor structures that can overcome the limitations of traditional designs. This includes concepts like gate-all-around (GAA) transistors and nanowire transistors.
• Three-Dimensional (3D) Transistors: Stacking transistors vertically in a 3D configuration to increase transistor density on a chip without reducing individual transistor size.
• Beyond CMOS: Exploring alternative transistor technologies besides the complementary metal-oxide-semiconductor (CMOS) design that has dominated the industry. Technologies like spintronics and tunnel FETs are potential areas of research.
• Neuromorphic Computing: Creating transistors that mimic the behaviour of neurons in the human brain, potentially leading to more energy-efficient and intelligent devices.
• Nanotechnology: Utilising nanomaterials and fabrication techniques to create transistors with atomic-level precision.