151 capacitor value
150 pF
150 pF · 0.15 nF · 0.00015 µF
| Marked code | 151 |
| Picofarads | 150 pF |
| Nanofarads | 0.15 nF |
| Microfarads | 0.00015 µF |
| Farads | 1.50e-10 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:
15 × 101 = 150 pF
So 151 is 15 followed by 1 zero: 150 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 151 is stocked as 0.00015 µF and the two numbers look nothing alike.
What 150 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 150 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 21.22 MΩ |
| 1 kHz — audio | 1.06 MΩ |
| 100 kHz — switching | 10.61 kΩ |
| 10 MHz — RF | 106.1 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 151K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 150 pF means |
|---|---|---|
151J | ±5% | 142.5 pF to 157.5 pF |
151K | ±10% | 135 pF to 165 pF |
151M | ±20% | 120 pF to 180 pF |
151Z | +80% / −20% | 120 pF to 270 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 151Z can legitimately be anything from 120 pF to 270 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 150 pF turns up
Hundreds of picofarads is filtering at radio frequencies and the timing element in fast oscillators. Below a nanofarad, a ceramic capacitor is close to ideal — very little loss, very little drift — which is why this range is used where accuracy matters.
Frequently asked questions
What is the value of a 151 capacitor?
150 pF — 150 pF · 0.15 nF · 0.00015 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 151 is 15 followed by 1 zero = 150 pF.
What is a 151 capacitor in µF?
0.00015 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 150 pF, 0.15 nF and 0.00015 µF are the same capacitor written three ways.
What does the letter after 151 mean?
Tolerance. 151K is ±10%, 151J is ±5% and 151M is ±20% — so a 151K is anywhere from 135 pF to 165 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 151 capacitor at 1 kHz?
1.06 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 10.61 kΩ at 100 kHz and 106.1 Ω at 10 MHz.
Nearby codes
- 181 capacitor — 180 pF
- 221 capacitor — 220 pF
- 271 capacitor — 270 pF
- 331 capacitor — 330 pF
- 391 capacitor — 390 pF
- 471 capacitor — 470 pF
- 561 capacitor — 560 pF
- 681 capacitor — 680 pF
- 821 capacitor — 820 pF
- 102 capacitor — 1 nF