A bypass capacitor is a component used in electronic circuits to filter high-frequency noise and stabilize power supply lines. It is also termed a "decoupling capacitor."
Function:

  • Noise Filtering: Shunts high-frequency signals (e.g., transient currents from digital ICs) to ground, ensuring clean DC voltage.

  • Voltage Stabilization: Acts as a local charge reservoir near IC power pins, reducing voltage dips during sudden current demands.

  • Signal Integrity: Prevents signal distortion and oscillations in high-speed circuits.
    Working Principle:

  • The capacitor’s impedance (Z=12πfC) decreases with frequency, making it effective at shorting high-frequency noise.

  • A combination of capacitors (e.g., 0.1µF ceramic + 10µF electrolytic) filters a broad frequency range.
    Applications:

  • Microcontrollers, processors, RF circuits, and power supply regulators.
    Technical Considerations:

  • Placement: Must be placed close to IC power pins to minimize parasitic inductance.

  • Capacitor Types: Ceramic (high-frequency), tantalum/electrolytic (low-frequency).

  • ESL/ESR: Equivalent Series Inductance (ESL) and Resistance (ESR) affect high-frequency performance.