1 µF capacitor (1,000 nF)
A 1 µF capacitor is the same as 1,000 nF or 1,000,000 pF. On ceramic and film parts it is printed as the code 105; schematics often write 1µ0 or 1u0.
How a 1 µF capacitor is marked
| Style | Marking | Where you see it |
|---|---|---|
| 3-digit code | 105 | Ceramic discs, multilayer ceramics, film capacitors |
| Code + tolerance | 105J · 105K · 105M | ±5% · ±10% · ±20% |
| Code + voltage | 1H105K · 2A105J | 50 V · 100 V film capacitors |
| IEC 60062 letter code | 1µ0 or 1u0 | Schematics, European parts (the letter is the decimal point) |
| Plain value | 1µF or 1MFD | Older US parts and electrolytics — bare decimals are µF |
| SMD (0402–1206) | usually unmarked | Check the reel label or measure with an LCR meter |
1 µF in every unit
| Picofarads | 1,000,000 pF |
|---|---|
| Nanofarads | 1,000 nF |
| Microfarads | 1 µF |
| Farads | 1 × 10^-6 |
Reactance of 1 µF
A capacitor's opposition to AC falls as frequency rises: XC = 1 ÷ (2π f C). This tells you whether 1 µF 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 | 3.18 kΩ |
| 60 Hz | 2.65 kΩ |
| 1 kHz | 159 Ω |
| 10 kHz | 15.9 Ω |
| 100 kHz | 1.59 Ω |
| 1 MHz | 0.159 Ω |
| 10 MHz | 0.0159 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 1 µF
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 | 100 µs | 500 µs | 1.59 kHz |
| 1 kΩ | 1 ms | 5 ms | 159 Hz |
| 10 kΩ | 10 ms | 50 ms | 15.9 Hz |
| 100 kΩ | 100 ms | 500 ms | 1.59 Hz |
Choosing a 1 µF capacitor
| Usual dielectric | X7R/X5R ceramic, tantalum, small electrolytic |
|---|---|
| Common voltage ratings | 10–50 V |
| Neighbouring E6 values | 330 nF, 470 nF, 680 nF, 1.5 µF, 2.2 µF, 3.3 µF |
1 µF is the most common input and output capacitor for small LDO regulators. Ceramic 1 µF parts are marked 105 (or not marked at all in SMD form), while electrolytic and tantalum parts print 1µF and a voltage. Check the regulator datasheet: some older LDOs need a minimum ESR and are unstable with a ceramic capacitor.
FAQ
What is the code for a 1 µF capacitor?
105. The first two digits (10) are picofarads and the third (5) is the number of zeros: 1,000,000 pF. In IEC letter notation it is written 1µ0 or 1u0.
Is 1 µF the same as 1,000 nF?
Yes. 1,000,000 pF = 1,000 nF = 1 µF; they are three names for the same capacitance.
What is the reactance of a 1 µF capacitor?
Xc = 1 ÷ (2π × f × C). At 1 kHz a 1 µF capacitor has 159 Ω; at 50 Hz 3.18 kΩ.
What cutoff frequency does 1 µF give with 10 kΩ?
fc = 1 ÷ (2π × 10 kΩ × 1 µF) = 15.9 Hz, and the time constant τ = R × C = 10 ms.