The IC that processes continuous natural analog signals such as light, sound, speed, and temperature is called an analog IC. These signals processed by analog ICs have continuity and can be converted into sine waves for research. And the digital IC processes discontinuous signals, which are all pulse square waves.
Analog ICs are divided into linear ICs that only process analog signals and hybrid ICs that simultaneously process analog and digital signals according to their technical types. Analog ICs can be divided into standard analog ICs and special application analog ICs based on their applications. Standard analog ICs include products such as amplifiers, voltage regulators/references, signal interfaces, data conversions, and comparators. Special application type analog ICs are mainly applied in four fields, namely communication, automotive, computer peripherals, and consumer electronics.
Analog ICs have four main characteristics:
a. The life cycle can reach up to 10 years.
Digital IC emphasizes the ratio of computing speed to cost, and the goal of digital IC design is to achieve the target computing speed at the lowest possible cost. Designers must constantly adopt more efficient algorithms to process digital signals, or utilize new processes to improve integration and reduce costs. Therefore, the lifecycle of digital ICs is very short, approximately 1-2 years.
Analog ICs emphasize high signal-to-noise ratio, low distortion, low power consumption, high reliability, and stability. Once a product reaches its design goals, it has long-term vitality, and there are many analog IC products with a life cycle of over 10 years. For example, the audio operational amplifier NE5532 has been one of the most commonly used audio amplification ICs since its launch in the late 1970s. Almost 50% of multimedia speakers use NE5532, with a lifespan of over 25 years. Due to its long lifecycle, the price of analog ICs is usually low.
b. Special process with minimal use of CMOS technology
Digital ICs often use CMOS technology, while analog ICs rarely use CMOS technology. Because analog ICs usually need to output high voltage or high current to drive other components, and the driving ability of CMOS technology is very poor. In addition, the key to simulating an IC is low distortion and high signal-to-noise ratio, both of which are relatively easy to achieve under high voltage. The CMOS process is mainly used in low voltage environments below 5V and continues to develop towards low voltage.
Therefore, in the early stages of simulating ICs, the Bipolar process was used, but the power consumption of the Bipolar process was high, resulting in the emergence of the BiCMOS process, which combines the advantages of both the Bipolar process and the CMOS process. In addition, there is a CD process that combines CMOS and DMOS processes. The BCD process combines the advantages of Bipolar, CMOS, and DMOS processes. In the high-frequency field, there are also SiGe and GaAS processes. These special processes require the cooperation of wafer foundries and familiarity of designers, while digital IC designers generally do not need to consider process issues.
c. Closely related to components
Analog ICs need to have good current amplification characteristics, small current characteristics, frequency characteristics, etc. throughout the entire linear working area; In design, due to the needs of technical characteristics, it is often necessary to consider the symmetrical structure of component layout and the matching form of component parameters; Analog ICs must also have low noise and low distortion performance. Resistors, capacitors, and inductors can all produce noise or distortion, and designers must consider the impact of these components.
For digital circuits, there is no noise or distortion, and digital circuit designers do not have to consider these factors at all. In addition, due to technological limitations, analog circuit design should minimize or eliminate the use of resistors and capacitors, especially high resistance resistors and large capacity capacitors, in order to improve integration and reduce costs.
d. Less auxiliary tools and longer testing cycles
Analog IC designers require both comprehensive knowledge and long-term experience accumulation. Analog IC designers need to be familiar with IC and wafer manufacturing processes and processes, as well as the electrical and physical characteristics of most components. Usually, few designers are familiar with the manufacturing processes and processes of ICs and wafers. In terms of experience, analog IC designers require at least 3-5 years of experience, while excellent analog IC designers require 10 years or even more of experience.
There are few auxiliary tools for analog IC design, and the EDA tools available are far less than those for digital IC design. Due to the high power consumption and multiple factors involved in analog ICs, which must maintain high stability, the certification cycle is long. In addition, the simulation IC testing cycle is long and complex.
Some analog IC products require special processes and packaging, and must be jointly developed with the wafer factory, such as BCD process and 30V high-voltage process. In addition, some products require WCPS wafer level packaging, and there are currently not many packaging factories with this technology.
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