100 pF capacitor (0.1 nF)
A 100 pF capacitor is the same as 0.1 nF or 100 pF. On ceramic and film parts it is printed as the code 101; schematics often write n10 or 100p.
How a 100 pF capacitor is marked
| Style | Marking | Where you see it |
|---|---|---|
| 3-digit code | 101 | Ceramic discs, multilayer ceramics, film capacitors |
| Code + tolerance | 101J · 101K · 101M | ±5% · ±10% · ±20% |
| Code + voltage | 1H101K · 2A101J | 50 V · 100 V film capacitors |
| IEC 60062 letter code | n10 or 100p | Schematics, European parts (the letter is the decimal point) |
| Plain value | 100 or 100pF | Older US parts and electrolytics — bare decimals are µF |
| SMD (0402–1206) | usually unmarked | Check the reel label or measure with an LCR meter |
100 pF in every unit
| Picofarads | 100 pF |
|---|---|
| Nanofarads | 0.1 nF |
| Microfarads | 0.0001 µF |
| Farads | 1 × 10^-10 |
Reactance of 100 pF
A capacitor's opposition to AC falls as frequency rises: XC = 1 ÷ (2π f C). This tells you whether 100 pF passes or blocks a signal — a decoupling capacitor needs a low reactance at the noise frequency, a coupling capacitor at the lowest signal frequency.
| Frequency | Reactance XC |
|---|---|
| 50 Hz | 31.8 MΩ |
| 60 Hz | 26.5 MΩ |
| 1 kHz | 1.59 MΩ |
| 10 kHz | 159 kΩ |
| 100 kHz | 15.9 kΩ |
| 1 MHz | 1.59 kΩ |
| 10 MHz | 159 Ω |
Real capacitors stop behaving like ideal ones above their self-resonant frequency, which depends on the package and lead length, so treat the high-frequency rows as an upper bound on performance.
RC time constant and filter corner with 100 pF
With a resistor R, the capacitor charges to 63% in one time constant τ = R × C and to over 99% in 5τ. The same pair makes a first-order low-pass or high-pass filter with corner frequency fc = 1 ÷ (2π R C).
| Resistor | τ = RC | 5τ (≈ full charge) | Corner fc |
|---|---|---|---|
| 100 Ω | 10 ns | 50 ns | 15.9 MHz |
| 1 kΩ | 100 ns | 500 ns | 1.59 MHz |
| 10 kΩ | 1 µs | 5 µs | 159 kHz |
| 100 kΩ | 10 µs | 50 µs | 15.9 kHz |
Choosing a 100 pF capacitor
| Usual dielectric | C0G/NP0 ceramic |
|---|---|
| Common voltage ratings | 50 V |
| Neighbouring E6 values | 33 pF, 47 pF, 68 pF, 150 pF, 220 pF, 330 pF |
At 100 pF a C0G (NP0) ceramic is the right choice: its capacitance hardly changes with temperature or voltage, which matters in RF tuning, oscillators and op-amp feedback compensation. Values this small are also affected by the stray capacitance of the board (a few pF), so keep leads and traces short.
FAQ
What is the code for a 100 pF capacitor?
101. The first two digits (10) are picofarads and the third (1) is the number of zeros: 100 pF. In IEC letter notation it is written n10 or 100p.
Is 100 pF the same as 0.1 nF?
Yes. 100 pF = 0.1 nF = 0.0001 µF; they are three names for the same capacitance.
What is the reactance of a 100 pF capacitor?
Xc = 1 ÷ (2π × f × C). At 1 kHz a 100 pF capacitor has 1.59 MΩ; at 50 Hz 31.8 MΩ.
What cutoff frequency does 100 pF give with 10 kΩ?
fc = 1 ÷ (2π × 10 kΩ × 100 pF) = 159 kHz, and the time constant τ = R × C = 1 µs.