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As technologies advance, digital circuits are becoming highly common in all PCBs, and the usage of analogue circuits is decreasing. However, there are some applications where we still use analogue circuits, which seem like going decades back in time. While designing your PCB, you might think it is better to use analogue circuits on PCB or not.
You must consider all the circumstances, including circuit application and component requirements. In this way, the final PCB will be efficient in every aspect.
The analogue circuits are also known as linear circuits, and they usually use only a few components, including the simplest ICs. These work on analogue signals, so there is no need to convert signals as digital circuits do. These circuits are generally used for devices that take input from the environment and pass the output directly to the environment after processing.
When it comes to the differences between analogue and digital circuits, there are many technical and non-technical differences between these two. The top 3 most important differences between these two include the following:
The analogue circuits are less immune against noise interference as compared to the digital circuits. It is because digital circuits work on binary signals while analogue signals work on variations in signal values making these much more susceptible to slight noise interferences. The working of analogue circuits can also generate noise during operations like modulation, transmission, amplification, reception, etc.
The analogue circuits are costly and intricate due to their lack of efficiency and accuracy. Digital circuits, on the other hand, are easier to design, manufacture, and implement, making them cost-effective and efficient.
The information integrity is much better with the analogue circuits as they directly take data, process it, and give the output. On the other hand, digital circuits need converters to convert data for their usage, and once they use data, it needs to be converted again. These conversions can create data loss affecting information integrity.
Some pros of using analogue signals include the following:
One major benefit of using analog circuits is that the signals are easier to process. For most circuits where environmental components are used with digital circuits, conversions are done wherever signal input and output happen.
It is because the circuit and other components are incompatible with the same type of signals. With an analogue circuit, that's not the case, as the input signal can be used, and processes and output can be generated easily.
Analogue circuits use analog signals that provide refined information with a higher frequency range and density. Whether you consider using these circuits for audio-related applications, heat, or image-related applications, this higher density signal range will always give more precise results with efficiency as no conversions are happening with these circuits.
Digital signals require high bandwidth because they must process the data at higher speeds. Thus, these result in some applications' lack of power and hardware utilization efficiency. On the other hand, analogue circuits are beneficial in both terms because they need less hardware and power due to their less bandwidth requirements.
Thus, analogue circuits are easily the better choice for many applications where top-end hardware and extensive power resources are unavailable.
Analogue circuits are mostly applicable in circuits that deal with environmental and physical elements like sound, temperature, pressure, position, or light. As there is no need to convert the circuit signal information, the outputs can be much more accurate and reliable.
With no binary data, even the slightest of chances can be more accurately represented with these circuits than the digital circuit.
PCBs made for communication systems having analogue circuits provide better than digital circuits. It is because these are better with their electrical tolerance, which is way less sensitive than in digital circuits. Thus, better results can be achieved with high accuracy for every provided change in the input signal.
Some cons of using analogue signals include the following:
This data transfer may not be reliable if your circuits are spread over a large area. It is because analog signals can involve signal disturbances when the distance is increased between circuits and components. On the other hand, digital circuits keep their signals stable as the signals are binary, and any signal disturbance does not affect those signals.
Thus, analogue circuits may not be the right choice if your application needs data transmission over long distances.
Generation loss is an issue that is related to analogue signal recording. It is the cumulative deterioration of the signal quality because of the compatibility limitations between the recording electronics, circuit components, and storage medium.
The quality keeps degrading due to generation loss with every proceeding copy of the original data. Thus, considering generation loss according to your specific application is essential.
Analogue signals are prone to issues that can easily affect the output of your whole circuit. Noise and distortions can affect analog signals easily, unlike digital signals, which cannot be affected that easily. Thus, analogue signals come with lesser immunity as compared to digital signals.
Even though digital signals are only binary, they can be either a 0 or a 1, and they are much better in quality than the analogue signals. These signals cannot be affected easily by undesired elements, including signal interferences, generation loss, distances, etc.
On the other hand, analogue signals include a wide range of data frequencies, but they lack quality because of the external factors affecting them.
Analogue circuits are usually used where the input and output are directly related to environmental factors. So, some of the applications of analogue circuits are:
With analogue circuits implemented in your PCBs, you must avoid all errors to get the best efficiency and perfect results. With these design practices, you can achieve accurate results from your PCBs while using analog circuits in your PCBs.
The analog signals within a circuit must be short and direct, so the best way to make this possible is to place the components within the circuit tightly. It is a part where your circuit design needs to be perfect for simplifying the direct routing of circuit traces.
Keeping the noise component of the analogue circuit towards the center is important as it may help other components hinder that noise.
One major issue with analogue circuitry is that the signals can cause reflections because of impedance mismatches at high frequencies. These reflections create electromagnetic interferences with other components on the PCB.
So, keeping signals and traces as short as possible is a good way to solve this problem. Keeping the circuit traces on one layer will help reduce the chances of such reflections.
The signals of both analogue and digital circuits can interfere with each other because of the noise. So, the best way to design your circuit is to keep them separated as much as possible.
Where there are traces of analogue circuitry, it will be best to avoid routing the high-speed traces of digital circuits in that area. In this way, both signals will stay safe from any type of interference.
The signal return paths for analogue circuits must be straight and clear. Keeping them as unobstructed as possible is best. If the direct return path is blocked, the return signal may wander at the ground plane to find the shortest path to the source, which can generate unnecessary noise.
So, it is necessary to provide clear signal return paths that are not blocked with plane splits, vias, slots, or cutouts.
The ground in PCBs works differently for digital signals and analogue signals. The ground for digital signals deals with high-speed signal returns and filters the power spikes created by the rapid switching of digital components.
This movement of digital signals can interfere with the analogue circuit signals when the ground is kept the same. So, the best way is to separate ground for analogue signals, which helps keep them isolated from digital signal interferences.
Is it better to use analogue circuits on PCB? There are certain advantages, but there are some disadvantages to these circuits. However, there are some specific applications where these make a better option as compared to digital circuits.
So, when deciding which circuits to use, it is better to consider the requirements of your PCB and the efficiency of both circuit types to decide which would make a better option.