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Basic Components - Capacitors

Unit Conversion

\[1F=1\cdot10^3mF=1\cdot10^6\mu F=1\cdot10^9nF=1\cdot10^{12}pF\]

Capacitor Selection

  • Voltage Rating: For derating purposes, select 10V for 3.3V, 10V for 5V, 25V for 12V, 50V for 24V, and 100V for 48V.

Capacitor Material Classification

Aluminum Electrolytic Capacitor Tantalum Capacitor Ceramic Capacitor
Capacitance 0.1uF-3F 0.1uF-1000uF 0.5pF-100uF
Polarity Yes Yes No
Voltage 5V-500V 2V-50V 2V-1000V
ESR Several tens of milliohms - 2.5 ohms Several tens of milliohms - several hundreds of milliohms Several milliohms - several hundreds of milliohms
ESL Less than 100nH Around 2nH 1-2nH
Frequency Range Low-frequency filtering, less than 600KHz Mid-low frequency filtering, several hundred KHz to several MHz High-frequency filtering, several MHz to several GHz
Weakness Narrow temperature range, electrolyte evaporation, heat generation caused by ripple current Must be derated, otherwise it will explode Welding temperature shock can easily cause failure, poor bending resistance, significant temperature difference between different materials
Suggestion Used for energy storage, in environments below 75℃, not recommended for high-frequency switching power supplies Voltage withstand should be selected at 2 times; Filtering with DC voltage above 15V is not recommended, especially in cases where the power supply changes rapidly, surge impact failure is significant Wiring should not be placed in stress areas, avoid high-temperature areas.

Uses of Capacitors


To remove noise. Large capacitors filter low frequencies, while small capacitors filter high frequencies.

Decoupling / Bypassing

Simply put, bypass capacitors are placed near the power supply, while decoupling capacitors are placed near the chip.

The purpose of decoupling/bypass capacitors is to bypass high-frequency noise in the system to GND. Typically, a small-value capacitor (typically 0.1uF) is connected in parallel between the power supply pin and GND to filter out high-frequency noise and ensure a stable and clean voltage.

The difference between decoupling and bypass capacitors is that decoupling capacitors are used to filter out interference in output signals (such as the output pin of a voltage regulator), while bypass capacitors are used to filter out interference in input signals (such as the power supply pin of a microcontroller). Decoupling capacitors are generally larger (above 10uF), while bypass capacitors are selected based on the resonance frequency (0.1/0.01uF).


Tuning capacitors are used to adjust the frequency of an oscillating circuit to resonate with another circuit that is already oscillating.


The purpose of coupling capacitors is to block DC and allow AC to pass through. The capacitor, together with the load connected to it, forms a filter that filters out low-frequency signals and retains high-frequency signals, creating a high-pass filter.

Coupling capacitors are used to connect two circuits and only allow AC signals to pass through by charging and discharging the capacitor, transmitting the signal to the next stage of the circuit.

Energy Storage

Energy storage capacitors are used to collect and store charges for later use.

Considerations for Choosing Capacitors

Pay attention to the voltage rating, and do not reverse the polarity of polarized capacitors.

References and Acknowledgments

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