Digital Integrated Circuits
Digital integrated circuits (ICs) contain millions or billions of transistors, capacitors and logic gates on a single piece of silicon called a chip. They are the reason our computers, mobile phones and many other electronic devices work so well.
After the design has been developed at a high level in hardware description languages, it is translated into a gate-level netlist by floorplanning methods. This stage also includes functional verification to ensure the implementation meets design goals.
1. Transistors
A key part of any digital integrated circuit, a transistor is an electronic semiconductor that is capable of switching, amplifying, and generating electrical signals. Its ability to control electron flow in a solid state – as opposed to the vacuum tubes of old – has revolutionized the world of electronics, and the transistor is now used in virtually every device that operates electronically.
It’s no wonder that the transistor has been credited with being one of the most important inventions of the 20th century. It has paved the way for major technological advances such as Moore’s Law, which states that the number of transistors on a chip doubles every two years.
Transistors are used in many different applications, but most commonly to handle discrete signals containing binary values (a time series that represents a sequence of quantities). They are used in logic circuits such as AND, OR, and NOT. They are also used in comparator circuits for comparing inputs and producing outputs based on those comparisons. They are also found in digital-to-analog converters and timing/clock circuits.
A transistor consists of three parts called the base, emitter, and collector, although modern switching devices have four terminals known as the gate, drain, and source. The transistor’s internal structure is arranged in layers, which are etched using photolithography – a process that uses photons of a specific wavelength to expose regions of material.
2. Diodes
Diodes allow electric current to flow in one direction (the forward direction) but block it in the opposite direction, essentially acting like an electronic version of a check valve. Diodes are used for a number of different functions in electronic circuits including converting alternating current to direct current and extracting modulation from radio signals.
A typical diode has two terminals referred to as the anode and cathode. A thin layer of semiconductor material separates these regions with a fixed voltage drop across the device, called the forward voltage drop or VF. This voltage drop is caused by the presence of free electrons that have a negative electrical potential on the anode side of the diode, known as the depletion region. The forward voltage drop is proportional to the current that passes through the diode.
Ideally, a diode would consume zero power when conducting forward current and block all reverse current. However, buck switching regulator in reality, this isn’t the case. In fact, a real diode will consume a small amount of power when conducting forward current and can leak some reverse current for a short time.
Because of this, diodes are used to help protect other electronic devices by blocking high-voltage spikes from reaching sensitive components and damaging them. Diodes that are designed specifically for this purpose are often referred to as transient voltage suppressors (TVS). They act like an electrical check valve to short out the spike and protect other electronic components.
3. Microprocessors
The microprocessor is a key component of digital integrated circuits. It contains the arithmetic, logic and control circuitry that performs the functions of a digital computer’s central processing unit. This includes interpreting and executing program instructions and handling arithmetic operations.
Unlike vacuum tubes that used multiple separate components, ICs combine transistors and other electrical devices on a single piece of solid material the size of a fingernail. These electronic components are connected by thin paths of metal, such as aluminum or copper, that act as wires. The invention of this technique by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor in 1958 made the modern world of information technology feasible.
Today, microprocessors and other ICs are found in everything from personal computers to cell phones to mainframes and supercomputers. Despite their small size and power consumption, they provide huge computing power.
As integrated circuit technology developed, it became possible to place more and more transistors on a chip. This allowed the size of data objects, called words, to increase from 4- and 8-bit words up to today’s 64-bit words. It also enabled the inclusion of a floating-point unit on the microprocessor chip, which sped up arithmetic calculations that previously had to be performed by software.
As a result, the microprocessor has become a core component of most personal computers and many other electronic devices. It has its own non-volatile memory for programs (ROM) and data (RAM). It also contains input/output ports.
4. Memory
Memory is a key part of any digital integrated circuit power management and is used to store the operating system and other software in a smartphone, tablet or calculator. It also stores information and data to be retrieved by the user later. As analog and mechanical devices are being converted to digital, such as smart doorknobs and stoves, it will further expand the market for memory-integrated circuits.
In a digital integrated circuit, the data is stored on the surface of a semiconductor chip in arrays of cells that each contain a capacitor and a transistor, which are switched on or off to store a binary value, 0 or 1. When the IC is read by a computer it can decode the values as either one of two states. This is a fundamental difference between digital and analog signals, which work at varying levels and have more complex waveforms than simple on or off.
Once the gate-level netlist is synthesized and verified, a physical layout is created by placing the gates and memory blocks on a silicon die using various floorplanning techniques. Routing automation scripts and software may be used at this stage to ensure that the IC is connected in accordance with design goals. Depending on the complexity of the IC, some portions may be laid out manually; other parts, such as memory and external IP cores, can be placed automatically by using scripts and automated software processes.