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Role of Chip Capacitor in Circuit
2019/10/17 03:10:59


Chip capacitor is the most commonly used component in circuit design, and it’s one of the passive components. Capacitors also often play an important role in high-speed circuits, such as the role of bypass, decoupling, smoothing, energy storage, oscillations completing, synchronization, and time constants.


1. DC: Let alternating current pass while blocking direct current.


2. Coupling: As a connection between two circuits, allowing the AC signal to pass through and transmit to the next level of the circuit.


3. Smoothing: the larger the frequency, the smaller the impedance of the capacitor. When frequency is low, due to the impedance of capacitor is relatively large, the useful signal can pass smoothly; When the frequency is high, due to the impedance of capacitor has been very small, it shorted out the high frequency noise to GND


Role of smoothing: the ideal chip capacitor, the larger the capacitance, the smaller the impedance, the higher the frequency of passage. Electrolytic capacitors are generally more than 1uF, in which the inductive component is very large, so the frequency is high, but the impedance will be large.


4. Tuning: System tuning of frequency-related circuits, such as mobile phones, radios and televisions.


The resonant frequency of the LC-tuned oscillating circuit is a function of the LC, and the ratio of the maximum and minimum resonant frequency of the oscillating circuit varies with the square root of the capacitance ratio.

The capacitance ratio here refers to the capacitance ratio between the capacitance with the minimum reverse bias voltage and the capacitance with the maximum reverse bias voltage. Therefore, the tuning characteristic curve of the circuit is basically a parabola.


5. Energy storage: Store electrical energy, used to release when necessary, such as camera flash, heating equipment and so on.


6. Bypass (Decoupling): for the AC circuit of some parallel components to provide a low-impedance access.


Bypass capacitor, a energy storage component that provides energy for a device. It utilizes the frequency impedance characteristics of capacitors (the frequency characteristics of the ideal capacitor are with the frequency increase, the impedance decreases), can make the output voltage output evenly, reduce the load voltage fluctuations.


Decoupling capacitors are components that filter out the interference of the output signal. Decoupling capacitors are equivalent to batteries, using their charge and discharge so that the enlarged signal is not disturbed by a sudden change in current. Its capacity depends on the frequency of the signal, the degree of suppression of ripples, decoupling capacitor plays a "battery" role, to meet the driving circuit current changes, to avoid coupling interference between each other.


The difference between bypass capacitors and decoupling capacitors is that the bypass is to filter out interference in the input signal, while the decoupling is to to filter out interference in the output signal, to prevent the interference signal from returning to the power supply.

7. Temperature compensation: In order to improve the stability of the circuit, compensation is made for the influence of other components on temperature adaptability.


Because the capacity of the timing capacitor determines the oscillation frequency of oscillator, the capacity of the timing capacitor is required to be very stable, and doesn’t change with the ambient humidity, so that the  oscillation frequency of oscillator can be stable. Therefore, the positive and negative temperature coefficients of capacitor release, temperature complement each other.


When the operating temperature increases, the capacity of one chip capacitor is increasing, while the capacity of the other chip capacitor is decreasing, and the total capacity of the two capacitors is in parallel with the sum of its capacity, so the total capacity is basically the same because one capacity is increasing and the other is decreasing.


Similarly, when the operating temperature decreases, the capacity of one capacitor is decreasing and the other is increasing, the total capacity is basically the same, stabilizing the oscillation frequency, and achieving temperature compensation.


Chip capacitor produced by EXSENSE Electronic Technology Co., Ltd., with small size, thin thickness (thickness is generally 0.15~0.5mm), low equivalent series, low loss and so on, the application frequency can reach several GHz, which is suitable for small, microwave occasions.

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