Analog circuits and digital circuits are two important circuit systems in electronic engineering. They play a vital role in modern science and technology. Digital electronics developed from analog electronics, so although there are differences between them, they are also closely related.
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Analog circuits and digital circuits
Analog circuits are circuit systems that process continuously changing signals, represent input signals by manipulating continuous voltages or currents, and produce corresponding outputs. Digital circuits are circuit systems that process discrete states, represent input signals by manipulating digital signals (high and low levels), and produce corresponding outputs. Analog circuits process (amplify or weaken) signals through the amplification characteristics of components, while digital circuits process signals through combinational logic circuits (switching characteristics) such as logic gates and triggers.
Example: An audio amplifier is a typical analog circuit that receives a continuously changing sound signal as input and amplifies it into an audible audio output signal. A typical digital circuit is a binary adder, which receives two binary numbers as input and produces a binary output of their sum.
Therefore, analog circuits are mainly used in fields such as sound, image and real-time data processing, covering almost the entire electronic field; while digital circuits are mainly used in fields such as computing, communication and storage.
Transistor VS Binary Number
Diodes, triodes (switching states) and thyristors in analog electronics can correspond to binary numbers 0 and 1 in digital electronics respectively.
Continuity VS Discreteness
Analog circuits process continuously changing signals and can capture every subtle change of the input signal in real time. Digital circuits process discrete signals and can only take a limited number of states, usually high level ("1") and low level ("0"). Whether it is an analog circuit or a digital circuit, they require an input signal and generate a corresponding output signal.
For example: a clock displays an analog signal of time, which indicates that time changes continuously, while a digital clock displays a digital signal of time, which changes in fixed numerical increments (0, 1, 2...9)
Non-quantization VS quantization
Analog circuits can provide an infinite number of output states because the output signal can have an infinite number of values. Digital circuits use binary codes to represent different states and values, so the values of the output signal are limited and quantized.
Analog operation VS logical operation
Analog electronics amplifies, filters and modulates continuous signals through analog operations such as amplifiers, filters and mixers. Digital electronics uses logical operations such as Boolean algebra, logic gate circuits and combinational and sequential logic circuits to perform logical judgment, calculation and control on discrete signals.
Analog modulation VS digital modulation
The modulation methods of analog circuits are mainly AM, FM and PM. The corresponding modulation methods in digital circuits are ASK, FSK and PSK. In addition, digital circuits can also implement more complex modulation methods such as OFDM, QAM and MSK.
Analog Calculus VS Digital Calculus
Analog electronics can use the voltage and current characteristics of capacitors to calculate differentials and integrals. Digital electronics achieves integration through feedback from registers (continuously feeding back the output to the input and accumulating). Then, the analog differential corresponds to the digital differential, which is the value of the previous moment minus the value of the next moment (the increment is obtained), and the register is used to save the values at different moments, and then subtract.
Accuracy and Noise
Due to the continuity of analog circuits, the accuracy of their output is affected by factors such as device accuracy and noise. Digital circuits use discrete signals, and their output accuracy can be strictly controlled, and they have a high tolerance for noise.
System Complexity
Analog circuits are relatively complex because they involve actual electronic components and analog signal processing. Digital electronics are generally composed of multiple discrete components and communicate and control through connecting lines.
With the advancement of technology and the rise of deep learning, the application of analog circuits and digital circuits in fields such as artificial intelligence, machine learning, and the Internet of Things is also increasing.