Decoupling Capacitor Calculator
Calculate optimal bypass capacitor values for your ICs. Get recommendations based on power consumption and frequency.
Calculator
Lower impedance = better decoupling
C = 1 / (2π × f × Z)
Where f = frequency, Z = target impedance
How to Use This Calculator
This decoupling capacitor calculator helps you select the right capacitor value to filter noise at your target frequency while achieving your desired impedance.
- Select an Application Preset — Choose from common use cases like MCU, Op-Amp, or RF circuits
- Enter Target Frequency — The frequency of noise you want to filter
- Set Target Impedance — Lower impedance provides better filtering
- Click Calculate — Get the recommended capacitance and component suggestions
The Capacitor Impedance Formula
Understanding Capacitor Impedance
A capacitor's impedance decreases as frequency increases, making it an effective high-frequency short circuit. The formula calculates the minimum capacitance needed to achieve your target impedance at a specific frequency.
- Lower impedance = better noise filtering but larger capacitor needed
- Higher frequency = smaller capacitor needed for same impedance
- Self-resonant frequency (SRF) = above this, capacitor becomes inductive
Capacitor Types for Decoupling
| Type | Value Range | Frequency Range | Best For |
|---|---|---|---|
| MLCC C0G/NP0 | 1pF - 10nF | 1MHz - 1GHz+ | RF, high-speed digital |
| MLCC X7R | 100pF - 10µF | 10kHz - 100MHz | General decoupling |
| MLCC X5R | 1µF - 100µF | 100Hz - 10MHz | Bulk decoupling |
| Polymer | 10µF - 1000µF | DC - 1MHz | Low ESR power filtering |
| Electrolytic | 10µF - 10000µF | DC - 100kHz | Bulk energy storage |
Placement Guidelines
General Rules
- Place closest to IC pins — Minimize inductance of PCB traces
- Use multiple values — Provides broadband filtering
- Smaller values closer — High-frequency caps nearest to IC
- Short, wide traces — Reduce trace inductance
- Via directly to ground plane — Low-inductance return path
Typical Configuration
- 100nF — Standard decoupling, one per power pin
- 10µF — Bulk storage, one per IC or power domain
- 10pF - 100pF — High-frequency filtering for RF/high-speed
Frequently Asked Questions
Why use multiple capacitor values?
Each capacitor has a self-resonant frequency (SRF) where it provides minimum impedance. Above SRF, the capacitor becomes inductive. Using multiple values ensures low impedance across a wide frequency range.
What's the difference between X7R and C0G?
C0G (NP0) has stable capacitance over temperature and voltage but limited to smaller values. X7R offers higher capacitance but varies with temperature (±15%) and DC bias. Use C0G for precision/RF, X7R for general decoupling.
How close should decoupling caps be to the IC?
As close as possible — ideally within 3mm of the power pins. Every millimeter of trace adds inductance that reduces high-frequency effectiveness.
Verify Your Component Selections
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