What is an Analog IC?

Analog ICs are essential in today’s mobile, wireless and internet of things devices. They ensure fidelity/precision and provide inputs/outputs that are proportional to the information being sent or received.

They work well with signals that constantly vary in amplitude and frequency. In contrast, digital circuits only assign meaning to two levels: on and off.

Amplification

An analog IC manipulates continuous time signals that vary smoothly between zero and full power supply limits. These devices have a large range of applications such as amplifiers, switches and current regulators. They are also used in circuits that detect continuous environmental effects such as temperature, humidity and light. In order to perform these functions, an analog IC requires high levels of fidelity and precision.

This is due to the physical limitations of transistors and their interaction with the silicon substrate, packaging and other components. To overcome these challenges, innovative process and circuit engineers developed creative solutions to produce a wide variety of analog ICs such as the LM324 operational amplifier. These op amps combined multiple functions into a single package, reducing the number of components needed for complex circuits.

These circuits require an input voltage iin that produces a differential base current in two transistor pairs Q1 and Q2; this results in the summed differential output current gm, equal to (iin)(hfe / hie). As the output current gm increases with the input signal, the rate of change of the output voltage increases with a maximum value known as the slew rate.

Analog ICs are divided into two categories; those used in the signal chain, which includes comparators and analog-to-digital converters (ADC) and interface chips, and the power chain which manages the battery and electrical energy. The design of these ICs requires deep knowledge about component behavior, which makes them more difficult to design than digital ICs. This translates into a lower number of EDA tools available and more design experience required.

Filtering

The analog IC is the most basic type of chip. It is what makes computers, cell phones and other electronic devices work. It converts the electrical signals from nature into electronic signals (analog) and from digital to analog in order to process them and make them usable for the user. The digital IC then completes the final logic calculations and stores the data in memory.

The output level of an analog IC is proportional to its input level, and it can be represented on a graph as a straight line. This allows the IC to operate at very high speeds and with very little linear voltage regulator circuit power consumption. This enables the IC to be used for many applications such as calculators, clocks, microprocessor chips and even digital watches.

The precision demands of the analog IC have nurtured a generation of highly skilled circuit and process engineers. Their creative solutions to overcome the limitations of available technology have earned them rock star status in the silicon valley. The renowned Robert Widlar, who designed the famous uA709 operational amplifier for Fairchild Semiconductor, is a good example of this. He was known for his off-the-wall antics, including threatening to cut through bureaucracy with an axe and buying a sheep to trim National Semiconductor’s unkempt lawns.

Power Management

Analog ICs require power to operate. They use a network of conductors to deliver the necessary electrical energy designed on-chip. These are called power management circuits, and they ensure that the signals and circuitry in an IC work properly. Without these, digital devices like computers and mobile phones would not function. Power management ICs are the unsung heroes of our electronic systems.

In analog ICs, the signal-to-noise ratio and power consumption are more important than in digital ICs. This is because analog ICs require a continuous range of values, while digital ICs only have two possible outputs (inputs). In addition, analog ICs have a longer life cycle and a slow iteration, which makes them more expensive than digital ICs.

The circuit design phase of analog ICs includes floor planning, placing functional blocks, and determining the chip area. It also involves analyzing the effects of parasitics on signal integrity and power consumption. Once the analog IC circuit is designed, the designers must check it to ensure that it works as intended and is logically correct. This is known as logic versus schematic checking, and it can be time-consuming and difficult.

Fortunately, Synopsys offers a unified suite of tools that accelerates the design of analog ICs. The Custom Design Platform provides industry-leading circuit simulation performance, a fast and easy-to-use layout editor, and best-in-class technologies for parasitic extraction, reliability analysis, and physical verification. These tools help designers quickly meet analog design closure, and make sure their designs are ready for tape out.

Frequency Mixing

Analog ICs are used in a wide range of electronic devices and systems. These include wireless communication, consumer and industrial electronics, automotive electronics, medical equipment, photovoltaic and electro-optical components, and many other applications. Analog ICs must be able to sense continuous time signals and perform a series of operations to respond to them. This requires high fidelity and precision. It also requires low noise and distortion.

A mixer is an electronic circuit that adds or multiplies two signals in a non-linear fashion. The results appear at the output ports as frequencies equal to the sum and difference of the original signals. In this case the original signal at PORT1 and the frequency of the LO (local oscillator) at PORT2 combine to produce an IF output signal at PORT3.

Mixer noise figure is important because it characterizes the noise that the mixer introduces to the IF output signal. This noise can corrupt the signal, increase demodulation complexity and lead to error rates. Typical noise figures are around 3 dB. Isolation defines how RMS converter well the mixer blocks RF and LO input signal energy from reaching the IF output. This is important because in-band noise can contaminate the IF output and interfere with demodulation.

The high fidelity and precision requirements of analog ICs can be challenging to meet. Variation in the manufacturing process and the physical interaction of densely packed devices can cause signal distortions. This is particularly significant at advanced technology nodes, where there are a large number of transistors within a small area. This creates the need for careful layout to avoid signal interference, which is critical to achieving high fidelity and precision.