PCB Blog - The difference between analog circuits and digital circuits in PCB board design

Analog circuits are circuit systems that deal with continuously varying signals by manipulating continuous voltages or currents to represent input signals and produce corresponding outputs. Digital circuits are circuit systems that deal with discrete states by manipulating digital signals (high and low levels) to represent input signals and produce corresponding outputs. Analog circuits process (amplify or attenuate) signals through the amplification characteristics of components, while digital circuits process signals through combinational logic circuits (switching characteristics) such as logic gates and flip-flops.

Analog and digital circuits are two important circuit systems in electronic engineering. They play a vital role in modern technology. Digital electricity is developed from analog electricity, so they are different but also closely related to each other.

Analog circuits

Difference between analog and digital circuits

Analog circuits are circuits that process analog signals; digital circuits are circuits that process digital signals.

An analog signal is a function of time,a continuously varying quantity,while a digital signal is a discrete quantity. Because all electronic systems are to specific electronic devices, electronic circuits as a carrier,in a signal processing, signal acquisition,signal recovery are analog signals, only the middle part of the signal processing is digital processing. Specifically, analog circuits mainly deal with analog signals,do not change with time,time domain and value domain are continuous signals, such as voice signals. Digital signals, on the contrary, is changing, digital signal processing including signal sampling,signal quantization,signal coding.

Take a simple example:

To come from a distance from a small to large sound,with amplitude modulation,analog signal transmission (accordingly,analog circuits should be used),then the amplitude of the signal will be more and more in the transmission process,because it is in the amplitude characteristics of electrical signals to simulate the sound of the characteristics of the strength of the weak.

However,if the digital signal transmission,we should use a code,each level of sound size corresponds to a code,in the sound input, every time you take a sample, the corresponding code will be transmitted out.It can be seen that no matter how many levels the sound is divided into,no matter how high the sampling frequency is,there is still a loss for the original sound in this way. However,this loss can be compensated for by increasing the sampling frequency,which is theoretically greater than twice the frequency of the original signal can be fully restored.

The levels of digital circuits are standardized, analog circuits are not.

Link between analog and digital circuits

The analog circuit is to supply power to the digital circuit while completing the execution of the actuator.

In analog and digital circuits, signals are expressed differently. Operations that can be performed on analog signals, such as amplification,filtering, and limiting,can be performed on digital signals. In fact, all digital circuits are fundamentally analog circuits, and their basic electrical principles, are the same as those of analog circuits. A complementary metal-oxide semiconductor is one that consists of two analog metal-oxide field-effect tubes, whose symmetrical, complementary structure makes it just right for handling high and low digital logic levels. However, digital circuits are designed with the goal of being used to process digital signals, and quantization noise may result if arbitrary analog signals are forced in without additional processing.

A function that represents the value of a signal at a set of discrete times is called a discrete-time signal. This is because the most commonly encountered discrete-time signals are analog signals sampled at uniform (and sometimes non-uniform) intervals in time. The terms "discrete time" and "digital" are often used to describe the same signal. Some of the theories of discrete-time signals also apply to digital signals.

How to realize the function of analog and digital circuits

Analog circuits and digital circuits they are also the carrier of signal changes, analog circuits in the circuit of the amplification and reduction of the signal is through the amplification characteristics of the components to achieve the operation, while digital circuits is the transmission of the signal is through the switching characteristics to achieve the operation.

In analog circuits, the changes of voltage, current, frequency, and period are mutually restrained, while in digital circuits the changes of voltage, current, frequency, and period in the circuit are discrete.

Analog circuits can operate at high current and high voltage, while digital circuits just operate at small voltage,small current bottom power consumption to complete or generate stable control signals.

With the advancement of technology and the rise of deep learning, analog circuits and digital circuits are increasingly being used in areas such as artificial intelligence, machine learning and the Internet of things.