689 capacitor value
6.8 pF
6.8 pF · 0.0068 nF · 0.000007 µF
| Marked code | 689 |
| Picofarads | 6.8 pF |
| Nanofarads | 0.0068 nF |
| Microfarads | 0.000007 µF |
| Farads | 6.80e-12 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 × 0.1 = 6.8 pF
The last digit here is 9, which is one of the two exceptions. Eight and nine do not mean 10⁸ and 10⁹ — they mean × 0.01 and × 0.1, and they exist so that values below ten picofarads can be written in the same three characters. Read literally, 689 would be 68 × 109 = 68,000 µF, which is not a ceramic capacitor and not what is in your hand.
What 6.8 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 6.8 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 468.1 MΩ |
| 1 kHz — audio | 23.41 MΩ |
| 100 kHz — switching | 234.05 kΩ |
| 10 MHz — RF | 2.34 kΩ |
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 689K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 6.8 pF means |
|---|---|---|
689J | ±5% | 6.46 pF to 7.14 pF |
689K | ±10% | 6.12 pF to 7.48 pF |
689M | ±20% | 5.44 pF to 8.16 pF |
689Z | +80% / −20% | 5.44 pF to 12.24 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 689Z can legitimately be anything from 5.44 pF to 12.24 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 6.8 pF turns up
Values of a few picofarads are trimming and compensation parts — tuning a crystal oscillator onto frequency, flattening the response of a probe, neutralising stray capacitance in an RF stage. At this size the capacitance of the board traces either side of the part is a serious fraction of the part itself.
Frequently asked questions
What is the value of a 689 capacitor?
6.8 pF — 6.8 pF · 0.0068 nF · 0.000007 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 689 is 68 followed by a divide rather than a multiply: 68 × 0.1 = 6.8 pF.
What is a 689 capacitor in µF?
0.000007 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 6.8 pF, 0.0068 nF and 0.000007 µF are the same capacitor written three ways.
What does the letter after 689 mean?
Tolerance. 689K is ±10%, 689J is ±5% and 689M is ±20% — so a 689K is anywhere from 6.12 pF to 7.48 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 689 capacitor at 1 kHz?
23.41 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 234.05 kΩ at 100 kHz and 2.34 kΩ at 10 MHz.
Nearby codes
- 829 capacitor — 8.2 pF
- 100 capacitor — 10 pF
- 120 capacitor — 12 pF
- 150 capacitor — 15 pF
- 180 capacitor — 18 pF
- 220 capacitor — 22 pF
- 270 capacitor — 27 pF
- 330 capacitor — 33 pF
- 390 capacitor — 39 pF
- 470 capacitor — 47 pF