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Method to Solve the Noise Interference of Power Supply on High-frequency PCB Board
Disassembly Skills of Chip Components on PCB
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What Are the Functions of Capacitors in Circuits?
Testing Techniques for Common Electronics Components
What to do if There is a Short Circuit on the PCB
Desoldering Principles and knowhow during PCBA Processing
Black Oxidation of the Inner Layer of the Multilayer PCB
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What Are the Differences Between PCB Paste Mask and Solder Mask?
How PCBA Is Packaged and Shipped
How long can PCBA finished products be stored?
What Are the Differences and Relations Between PCB, PCBA, and SMT?
PCB Baking Specifications
PCB "Solder Mask Tenting" and "Solder Mask Opening"
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Temperature zone standard for SMT reflow soldering
Small and medium volume PCB manufacturers in China
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For power filter, the more capacitors, the better?
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Content of PCB incoming testing
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What is Blind via and Buried via
PCBA Manufacturers Temperature and Humidity Sensitive Components Management
Why choose Shenzhen SMT processing factory?
How long does it take to calculate the quotation for PCBA manufacturing?
Introduction of PCB design clearance requirements
Explanation of BOM, DIP, SMT, SMD
Introduction of the process of PCBA prototype
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Factors that affect the Price of FPCB
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Skills of using 0ohm resistor in PCB design
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SMT processing solder joint quality inspection
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Compare of multi-layer PCB with single/double layer PCB
Why do we need to introduce so many subdivided GND
Difference between immersion gold boards and gold plating boards
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Classification of different GND in circuit
Why PCB baking is necessary during manufacturing process
The handle and precautions of OSP board in SMT process
How to choose capacitors for filter decoupling
How to choose filter capacitor for switching power supply
5 database need for SMT process
Function of three-terminal capacitor
Introduction of PCB OSP surface treatment
Method of inspecting the quality of SMT by step
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Pad shape influence on the strength and reliability of the soldering joints
The difference between high temperature solder paste and low temperature solder paste
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Manual visual inspection in PCBA processing
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The key points of quality control in PCBA processing
Common causes of solder beading during SMT process
Analysis of the advantages and disadvantages of HASL PCB surface
Requirements for layout of components during SMT assembly
Selection of electronic components and CCL for PCBA
Performance and appearance quality inspection of components.
Quality and Reliability of SMT Chip Processing and Production
Coupling and decoupling function of capacitor
Two methods to connect digital ground and analog ground
Common sense in SMT process

Coupling and decoupling function of capacitor

Capacitor is the commonly used component in a circuit. The role of the capacitor is filtering, bypass, coupling, decoupling, energy storage and so on. "Isolating DC and pass AC" is the most basic function of the capacitor. Today we are talking about two functions that are difficult to understand: "coupling" and "decoupling". Today, Shenzhen China PCBA manufacturer will talk about these two functions


1. Coupling

Capacitors have a coupling effect. Send the output signal of the previous circuit to the subsequent circuit, which is called coupling. It is a process of isolating DC and coupling AC. C2 and C3 in the picture below are coupling capacitors.

Capacitive coupling amplifier circuit

Capacitive coupling amplifier circuit


What is used here is capacitive coupling. In this way, the DC operating points of the front and rear circuit do not affect each other! If C2 and C3 are directly connected, this is called direct coupling, adding a capacitor is capacitive coupling. That is, the input AC signal is sent to the rear amplifier circuit through the capacitor for amplification, and the DC signal is isolated.


When the frequency is low, such as audio, the capacitor here may be replaced with a polar electrolytic capacitor. The direction of the negative terminal of polar electrolytic capacitor connected to ground. Why use electrolytic capacitors? Because the capacity of electrolytic capacitors is larger, the capacity of non-polar capacitors is generally smaller.


By the way, C1 in the figure is a filter capacitor to filter out the noise of the input signal. R1, C1 form a resistance-capacitance filter circuit.


Second, decoupling


What does decoupling mean? As mentioned earlier, coupling means that the signal is sent from the previous circuit to the subsequent circuit, which is called coupling. And decoupling, as the name implies, is to remove the useless signals that are coupled. Decoupling capacitors are generally placed at the output terminal of the power supply. As shown in the figure below, C27 is the decoupling capacitor. The value of this capacitance depends on the size of the interference signal coupled from the subsequent load end.

Because of some reasons at the load end, there will also be some majeure factors that cause voltage fluctuations. This voltage fluctuation will in turn affect the voltage of the power supply chip. The output capacitor decouples the voltage fluctuation coupled from the load end.


For example, when the load is running at full load, the current is very large. Sometimes there is no need to run at full load, the current will be small. At the moment of high current to small current conversion, the power chip will not have time to respond. This decoupling capacitor works, and stabilizes the voltage fluctuations coupled from the load. The power chip is not affected.