Integrated circuits (ICs) are synonymous with electronics. Wherever there is any electronic device, there is definitely one or more ICs. There is no electronics without ICs. Electronics has become so popular, widely acceptable, and ubiquitously applicable, all due to the invention of integrated circuits. Integrated circuits are miniaturized integration of complete electronic circuits on a single semiconductor chip. ICs are manufactured through rigorous and complex manufacturing processes. This is why ICs are highly reliable, suitable for large-scale production, have large circuits in extremely small dimensions, consume less power, and can be operated at high frequency and speed.
What is an integrated circuit?
The idea of integrated circuits was first contemplated when transistors were invented. Conventionally, electronic circuits were produced by assembling different discrete components and interconnecting them on a prototyping or printed circuit board. With the introduction of transistors, semiconductor technology took a complete leap forward, and researchers began finding ways to get not just transistors but entire electronic circuits onto a single silicon wafer. This was just the beginning.
The number of transistors and other electronic components that can be manufactured and interconnected on a single silicon wafer has begun to increase rapidly, nearly doubling every two years. This is popularly known as Moore's Law. Since 1965 when Moore's law was predicted, it is still applicable today in 2021. Currently, integrated circuits are microscopic or nanocircuits integrated on a single semiconductor chip. The heart of any IC is a die, on which a complete and functional large-scale electronic circuit is manufactured. The connections are brought out of this microscopic circuit, placed on a compact die as part of the IC packaging.
Unlike discrete circuits, the components manufactured in an IC cannot be disassembled or replaced. The circuit remains integrated as a single unit and cannot be modified. That's why these microscopic circuits on small data are called integrated circuits.
Types of integrated circuits
Integrated circuits are a complex form of electronics. They come in a wide range of features, packaging, applications and complexities. Still, it is possible to somehow classify various integrated circuits based on some broad classification factors.
Any integrated circuit is basically a miniaturization of an integrated electronic circuit. Therefore, the scale at which miniaturization is achieved is a criterion for classifying IC chips. This is determined by how many transistors or logic gates are integrated into a single IC. Based on chip size, integrated circuits are classified as follows –
- Small-scale integration
- Medium-scale integration
- Large-scale integration
- Large-scale integration
- Ultra-large scale integration
Another factor by which ICs are classified is by circuit type. After all, electronics is all about signals. Based on signal type, integrated circuits are classified as follows –
- Digital integrated circuits
- Analog integrated circuits
- Mixed-Signal Integrated Circuits
A third way to classify ICs is by their manufacturing technique. Based on this, integrated circuits are classified as follows –
- Thin and thick film ICs
- Monolithic ICs
- Hybrid/multichip ICs
Classification of ICs based on chip size
Integration scale has always been the inspiration and aspiration of the semiconductor industry. The integration scale denotes the number of transistors or gates integrated on a single chip. On this basis, integrated circuits are of the following type:
Small-Scale Integration – In the early days of IC technology, from 1961 to 1965, ICs had only a few components integrated on a chip, typically 2 to 10 transistors. Currently, integrated circuits with 10 to 100 transistors on a single chip, forming about 3 to 30 gates on the chip, are classified as small-scale integration ICs. These ICs are used to make flip-flops and logic gate ICs.
Medium Scale Integration – The next higher level of IC integration is medium scale, in which typically 100 to 1,000 transistors, forming 30 to 300 logic gates per chip, are manufactured on a single chip. Medium-scale integration technology was prominent between 1966 and 1971. This technology is used to make multiplexers, decoders, counters and registers.
Large-scale integration – From 1971 to 1979, large-scale integration (LSI) technology took over from MSI technology. In large-scale integration, thousands of transistors – typically 1,000 to 20,000 transistors, resulting in 300 to 3,000 gates per chip – are manufactured on a single chip. This technology is used to manufacture RAM, ROM and microprocessors.
Large-Scale Integration – From 1980 to 1984, large-scale integration (VLSI) was achieved. In VLSI technology, tens of thousands of transistors – typically 20,000 to 50,000 transistors forming 3,000 gates per chip – are manufactured on a single die. This technology is used to design 16-bit and 32-bit digital signal processors (DSP), RISC processors, microprocessors, and microcontrollers.
Ultra-Large Scale Integration – After 1984 and until now, ultra-large scale integration (ULSI) has been achieved. In ULSI technology, 50,000 to billions of transistors are manufactured on a single chip. ULSI technology is mainly used to design 64-bit and higher microprocessors and controllers.
The future of IC integration scale lies in nanotechnology. Moore's Law is still valid despite rising research and development costs. Semiconductor manufacturers are still, and probably always can, hope to achieve an even higher level of integration. Modern electronics applications (artificial intelligence, machine learning, deep learning, cloud computing, IoT, AIoT, augmented reality, mixed reality, holographic reality, supercomputing, scientific computing, etc.) are increasingly demanding on memory and also computational power. . The semiconductor industry may never reach a saturation point and the level of integration may never come to an end.
Classification based on signal type –
Electronics is all about signal processing. Thus, all electronic circuits, as well as integrated circuits, are classified into the following types:
Analog/Linear ICs – These integrated circuits are designed to process continuous signals. In these ICs, the input and output have a linear relationship. These ICs are designed for applications like operational amplifiers, differential amplifiers, timers, sensors, voltage regulators, analog multipliers, phase-locked loops, modulators, demodulators, audio filters, etc.
Digital ICs – These integrated circuits are designed to process digital signals, i.e. 0 or 1, HIGH or LOW, ON or OFF. These ICs have logic inputs and generate one or the other logic function. Digital ICs are the main products of the semiconductor industry. These ICs are designed for applications such as flip-flops, logic gates, counters, registers, multiplexers, decoders, encoders, microprocessors and microcontrollers.
Mixed-Signal ICs – These integrated circuits are designed to process combinations of analog and digital signals. These are the most complex to design, as analog and digital circuits have different power requirements, signal levels, and operation. These ICs are designed for applications such as analog-to-digital conversion, digital-to-analog conversion, Ethernet, radio, and power management.
Classification based on manufacturing
IC technology is the core of electronics. Integrated circuits are made possible by several rigorous manufacturing processes. Based on the manufacturing technique, integrated circuits are of the following type:
Thin and Thick Film ICs – In these types of integrated circuits, the passive components are manufactured on the chip, while the transistors and diodes are connected as separate components to form a single complete electronic circuit. These ICs are basically a combination of integrated and discrete components in a single package that offers a unified function. In thin film technology, passive components such as resistors and capacitors are manufactured in the IC by depositing a film of conductive material on a glass or ceramic substrate. By varying the thickness of the conductive material, passive electrical properties such as resistivity and capacitance are controlled. In thick film technology, the desired passive components are manufactured by depositing conductive material using silk printing technique onto a ceramic substrate. In this technique, circuit connections are made using conductive or dielectric pastes, and a mesh of stainless steel wires is used as a screen. After printing the circuit onto a ceramic substrate, it is fired in a kiln at high temperatures to infuse the circuit into the die.
Monolithic ICs – In a monolithic IC, all passive, active and discrete components are manufactured on a single silicon crystal. These are the most common types of ICs used today. They are easy to produce and highly reliable in operation. Although this is the most widely adopted IC manufacturing technique, it still faces many practical challenges. The most notable of these challenges are poor isolation, limited power, and signal noise.
Hybrid/Multi-Chip ICs – In these types of ICs, more than one individual chip is interconnected in a single package. Active components such as transistors and diodes and passive components such as resistors and capacitors are diffused into the chip and interconnected through metallic connections. These ICs are mainly used for high power applications (5W to 50W) or high performance applications. Hybrid ICs are better in technology and design compared to monolithic ICs.
Conclusion
Integrated circuits are the core of electronics. In this article, we only cover simple classifications of modern ICs. This only covers a small part of IC technologies. IC design and manufacturing processes are endless topics. There is much more to know about ICs. The future of integrated circuits lies in nanoelectronics. It's another vast and fascinating topic.