SMDコンデンサコード 読取りツール
数値コードとEIA-198表記
Required Parameters
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Quick Answer
SMD capacitor codes are in picofarads: the last digit is the multiplier (number of zeros). 104 = 100,000 pF = 100 nF = 0.1 µF. EIA-198 codes use a letter-digit-letter format for 1% precision parts.
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- 104 = 100 nF
- 473 = 47 nF
- 222 = 2.2 nF
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Design Notes
Most SMD ceramic capacitors (MLCCs) are unmarked. When marked, digit codes give capacitance in picofarads. The biggest practical concern is not the marking but the dielectric type: C0G/NP0 ceramics are stable but limited to small values, while X7R and X5R offer high capacitance but lose value with DC bias and temperature.
Common Mistakes
- 1
Assuming an unmarked SMD component is a capacitor — it could be a resistor, inductor, or even a diode in some packages.
- 2
Forgetting that MLCC capacitance drops significantly under DC bias (X5R 10µF at 10V may only be 3-4µF with 8V applied).
- 3
Using Y5V/Z5U dielectrics where stable capacitance is needed — their value can change by 80% with temperature.
Engineering Handbox
1. First two digits: 10 (significant figures in pF) 2. Last digit: 4 (add four zeros) 3. Raw: 10 + 0000 = 100,000 pF 4. Convert: 100,000 pF = 100 nF = 0.1 µF
Knowledge Base
コードの単位は？
ピコファラド（pF）。最後の桁=乗数。104 = 100,000 pF = 100 nF = 0.1 µF。
最も一般的なコードは？
104（100nF/0.1µF）— ほぼ全てのICのデカップリングに使われる標準値。
pF、nF、µFの変換は？
1 µF = 1,000 nF = 1,000,000 pF。各ステップ×1000。
なぜマーキングがないSMDコンデンサが多い？
ほとんどのMLCCは小さすぎて印字不可。BOMまたはLCRメーターで識別。
DC電圧で容量が変わる？
X7R/X5Rセラミックは印加電圧で容量低下。10µFが8V下で3〜4µFになることも。
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