680 capacitor value
68 pF
68 pF · 0.068 nF · 0.000068 µF
| Marked code | 680 |
| Picofarads | 68 pF |
| Nanofarads | 0.068 nF |
| Microfarads | 0.000068 µF |
| Farads | 6.80e-11 F |
Reading the code
The three digits are not a part number. The first two are the value in picofarads and the third says what to do with them:
68 × 100 = 68 pF
So 680 is 68 followed by 0 zeros: 68 pF. The code is always in picofarads even when the part is sold in microfarads, which is the whole difficulty with it — a capacitor marked 680 is stocked as 0.000068 µF and the two numbers look nothing alike.
What 68 pF does at frequency
A capacitor's opposition to a signal is its reactance, 1 ÷ (2πfC), and it falls as the frequency rises. Over the range of frequencies a circuit can put across it, a 68 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 46.81 MΩ |
| 1 kHz — audio | 2.34 MΩ |
| 100 kHz — switching | 23.41 kΩ |
| 10 MHz — RF | 234.05 Ω |
Ten times the frequency is a tenth of the reactance, every time — which is why choosing a decoupling capacitor is really choosing the frequency band you want it to be low-impedance across, and why boards carry several sizes in parallel rather than one large one.
The letter after the number
A code like 680K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 68 pF means |
|---|---|---|
680J | ±5% | 64.6 pF to 71.4 pF |
680K | ±10% | 61.2 pF to 74.8 pF |
680M | ±20% | 54.4 pF to 81.6 pF |
680Z | +80% / −20% | 54.4 pF to 122.4 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 680Z can legitimately be anything from 54.4 pF to 122.4 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 68 pF turns up
Tens of picofarads is the crystal load range: the two capacitors either side of a quartz crystal that set it oscillating at its marked frequency. Also RF tuning and the compensation capacitor round a fast op-amp.
Frequently asked questions
What is the value of a 680 capacitor?
68 pF — 68 pF · 0.068 nF · 0.000068 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 680 is 68 followed by 0 zeros = 68 pF.
What is a 680 capacitor in µF?
0.000068 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 68 pF, 0.068 nF and 0.000068 µF are the same capacitor written three ways.
What does the letter after 680 mean?
Tolerance. 680K is ±10%, 680J is ±5% and 680M is ±20% — so a 680K is anywhere from 61.2 pF to 74.8 pF and still in specification. A Z means +80%/−20%, which is not a mistake: some ceramic dielectrics really are that loose.
What is the impedance of a 680 capacitor at 1 kHz?
2.34 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 23.41 kΩ at 100 kHz and 234.05 Ω at 10 MHz.
Nearby codes
- 820 capacitor — 82 pF
- 101 capacitor — 100 pF
- 121 capacitor — 120 pF
- 151 capacitor — 150 pF
- 181 capacitor — 180 pF
- 221 capacitor — 220 pF
- 271 capacitor — 270 pF
- 331 capacitor — 330 pF
- 391 capacitor — 390 pF
- 471 capacitor — 470 pF