A practical guide to the 1pF capacitor: where it’s used in RF matching networks and oscillators, which package to choose, key specs like C0G dielectric and ±0.1 pF tolerance, and where to buy from major distributors.

A 1 pF capacitor is one of the smallest capacitance values you’ll encounter in electronics, and yet it shows up in some surprisingly demanding applications. If you’ve never had to deal with a 1 pF cap before, you might wonder whether something that small even matters. Once you’ve worked on RF circuits, antenna matching networks, or high-speed oscillators, you’ll know the answer is absolutely yes — and you’ll also know how easy it is to ruin your design by getting the footprint, dielectric, or parasitics wrong on a component this tiny.

This guide breaks down everything a PCB engineer needs to know about the 1pF capacitor: what it’s used for, which packages make sense, how to read the specs, and where to actually source them.

What Is a 1 pF Capacitor?

A 1 pF capacitor (one picofarad, or 1×10⁻¹² farads) is an extremely small-value capacitor used primarily in high-frequency analog and RF circuits. For context, a typical decoupling capacitor on a digital power rail is 100 nF — that’s 100,000 times larger than a 1 pF cap.

At this scale, the capacitance of the component is often comparable to — or smaller than — the parasitic capacitance of the PCB traces, solder pads, and even the IC pins themselves. That’s what makes working with 1 pF caps both powerful and tricky. The circuit topology and the physical layout matter just as much as the component value.

The value is sometimes written as 1p, 1pF, or in EIA code as 1R0 (though manufacturers vary on notation for sub-10 pF values — always check the datasheet).

Where Is a 1 pF Capacitor Used?

Most of the applications for 1 pF capacitors fall into a few well-defined categories. If you’re seeing this value in a BOM and wondering why it’s there, one of these is almost certainly the reason.

RF Impedance Matching Networks

This is the most common home for 1 pF caps. In L-network, pi-network, and T-network matching topologies, component values are calculated based on the source and load impedances and the target frequency. At frequencies above 1 GHz, even small impedance mismatches cause significant reflection loss, and the calculated capacitance often lands in the 0.5–5 pF range. A 1 pF cap in a matching network is doing real work.

Crystal Oscillator Load Capacitance

Quartz crystals have a specified load capacitance — typically 12 pF or 18 pF — that must be presented by the circuit for the crystal to oscillate at its marked frequency. The two capacitors in a standard Pierce oscillator circuit (one from each oscillator pin to ground) are chosen to present this load. In some high-frequency crystals or when parasitic capacitance is already significant, the external cap values can drop to 1–2 pF.

VCO Frequency Trimming

Voltage-controlled oscillators use a varactor diode whose capacitance shifts with applied voltage to tune the output frequency. Fixed capacitors placed in parallel with the varactor set the baseline capacitance of the tank circuit. At microwave frequencies, those trim caps can be as small as 1 pF.

Antenna Tuning and Filter Design

In small loop antennas and ceramic chip antennas, impedance matching at 2.4 GHz, 5 GHz, or cellular bands often requires very small shunt or series capacitors. The same applies to bandpass filter design using coupled resonators — 1 pF shows up frequently in filter topologies above 1 GHz.

High-Speed PCB Signal Coupling and Bypass

In some RF and mmWave designs, a 1 pF cap is used as an AC coupling element where higher capacitance would create too much low-frequency loading, or as a very high-frequency bypass where larger caps would resonate below the frequency of interest.

1 pF Capacitor Packages and Physical Dimensions

Package selection for a 1 pF cap matters more than it does for larger values. At 1 pF, the self-resonant frequency (SRF) is extremely high, but parasitic capacitance from the PCB land pattern can meaningfully alter the effective circuit capacitance. Smaller packages have lower parasitics.

Package	L × W (mm)	Typical Voltage Rating	Notes
0402 (1005M)	1.0 × 0.5	25–50 V	Most common for general RF use
0201 (0603M)	0.6 × 0.3	10–25 V	Lower parasitics, harder to place
01005 (0402M)	0.4 × 0.2	10 V	Minimal parasitics, reflow-only
0603 (1608M)	1.6 × 0.8	50–100 V	Lower SRF, usually overkill for 1 pF
ATC 100B series	Various	Up to 500 V	RF/microwave high-Q chip caps

For most RF work in the 1–6 GHz range, 0402 is the practical sweet spot — small enough that pad parasitics don’t swamp the 1 pF value, but large enough that assembly houses can handle it without special placement requirements. If you’re working at 10 GHz and above, 0201 or 01005 starts making sense.

Key Electrical Specs to Check on the Datasheet

A 1 pF capacitor datasheet has fewer obvious numbers than a bulk decoupling cap, but the parameters that matter are critical.

Parameter	What to Check	Why It Matters
Capacitance tolerance	±0.1 pF or ±0.25 pF (not %)	At 1 pF, a ±5% tolerance is meaningless — get absolute tolerance in pF
Dielectric type	C0G (NP0)	Only C0G is stable enough for RF; X7R drifts too much
Q factor / ESR	Q > 100 at target freq	Low Q degrades filter insertion loss and oscillator phase noise
Self-resonant frequency	Should be >> operating frequency	Typically >10 GHz for 0402 C0G at 1 pF
Voltage rating	25 V or higher	Usually not a concern at signal levels, but verify in high-power RF
Temperature coefficient	±30 ppm/°C or better	Critical in frequency-determining circuits

Always use C0G (NP0) dielectric for 1 pF capacitors. X7R and Y5V dielectrics have poor capacitance stability, especially at low values where the permittivity variation is a larger percentage of the total capacitance. Most reputable RF-grade 1 pF caps are C0G by default, but double-check before ordering.

Capacitance Tolerance: Why ±0.1 pF vs. ±5% Matters

This is a point that trips up engineers new to RF design. Standard capacitor tolerances are given in percentage (±5%, ±10%). But at 1 pF, ±5% means ±0.05 pF — which sounds fine until you realize that the parasitic capacitance of your PCB via might be 0.1–0.3 pF, making the component tolerance the least of your problems.

More practically: if you’re using a 1 pF cap in a matching network or filter and you specify ±5%, you might get a part that’s actually 0.95 pF or 1.05 pF. At 2.4 GHz, that 5% shift changes the reactance from ~66 Ω to ~63 or ~70 Ω — which in an impedance matching application can mean a measurable return loss difference.

For production designs, specify ±0.1 pF or ±0.25 pF absolute tolerance. The cost difference from standard tolerance is minimal.

Popular 1 pF Capacitor Part Numbers

Here are specific parts from major manufacturers that are well-characterized and widely stocked:

Manufacturer	Part Number	Package	Dielectric	Tolerance	Voltage
Murata	GRM1555C1HR10BA01D	0402	C0G	±0.1 pF	50 V
TDK	C1005C0G1H010C050BA	0402	C0G	±0.1 pF	50 V
Vishay	VJ0402A1R0CXACW1BC	0402	C0G	±0.1 pF	50 V
Kemet	C0402C109C5GACTU	0402	C0G	±0.1 pF	50 V
Würth Elektronik	885012005009	0402	C0G	±0.1 pF	50 V
AVX/Kyocera	04025A1R0BAT2A	0402	C0G	±0.1 pF	50 V
ATC	100B1R0BW500XT	ATC 100B	C0G	±0.1 pF	500 V

The ATC 100B series is worth knowing about if you’re doing power RF work — it’s a high-Q RF chip capacitor designed specifically for demanding microwave applications and has tighter RF performance specs than standard MLCC products.

PCB Layout Tips for 1 pF Capacitors

Getting the layout right is arguably more important than the component selection for a value this small.

Keep land patterns minimal. Oversized pads add capacitance to ground. Use the manufacturer’s recommended land pattern, not a generic one from your CAD library footprint database. A slightly too-large 0402 land pattern can add 0.05–0.2 pF of parasitic capacitance — that’s 5–20% of your intended 1 pF.

Avoid ground planes directly under the component. For capacitors in series signal paths, having a ground plane immediately beneath the cap adds shunt capacitance. Use a copper void (also called a moat or clearance) under the component footprint if the parasitic capacitance is a concern at your operating frequency.

Route traces to pads, not through them. Trace routing that loops around or extends past the cap pads adds inductance and capacitance. Come straight in to each pad with the minimum necessary trace width.

Minimize via use near 1 pF caps. A standard PCB via adds roughly 0.3–1 pF of capacitance depending on board stackup. One via placed too close to a 1 pF matching cap can completely detune your network.

Simulate with parasitic extraction before committing to a layout. Most RF-capable EDA tools (Cadence AWR, Keysight ADS, or even Sonnet Lite for free) allow you to extract parasitic capacitance from your layout. Run this before sending to fab if your design is frequency-sensitive.

Where to Buy a 1 pF Capacitor

These parts are widely stocked at major distributors. Use the parametric search filters to narrow by capacitance, dielectric, tolerance, and package.

Distributor	Search/Filter Link	Notes
Digi-Key	digikey.com	Largest stock, good parametric filters
Mouser	mouser.com	Strong on Murata, TDK, AVX
LCSC	lcsc.com	Budget-friendly, good for prototyping
Arrow	arrow.com	Authorized for most major brands
Farnell/Element14	farnell.com	UK/EU stocking, authorized distributor

For production quantities, going direct to the manufacturer (Murata, TDK, AVX) through their authorized distribution channels ensures traceability and avoids counterfeit risk — something that matters more than most engineers admit until they’ve been burned by fake passives.

Useful Resources and Datasheets

• Murata SimSurfing – Online simulation tool for Murata capacitors, shows S-parameters and impedance vs. frequency: ds.murata.com/simsurfing
• TDK Product Finder – Parametric search with downloadable SPICE and S-parameter models: product.tdk.com
• Kemet KSIM – Online capacitor simulation tool with ESR, ESL, impedance curves: ksim.kemet.com
• AVX SpiCap – S-parameter and SPICE model generator for AVX capacitors: avx.com/products/spicap
• ATC Microwave Capacitors Datasheet Library – High-Q RF chip caps with full S-parameter data: atceramics.com
• IPC-7351B – Land pattern standard for SMD components, including small passives
• Coilcraft RF Inductor/Capacitor Design Tools – Useful for LC filter and matching network calculations: coilcraft.com/tools

Frequently Asked Questions About 1 pF Capacitors

Why would I use a 1 pF capacitor instead of a larger value?

In RF and microwave circuits, the required component values are determined by the operating frequency and the impedances involved. At 2.4 GHz or higher, the reactance of even a few picofarads can be significant. In an impedance matching network or RF filter, using too large a capacitor would present too low an impedance and short-circuit the signal path at the operating frequency. The 1 pF value is specifically chosen to provide the right reactance at the target frequency.

Can I replace a 1 pF capacitor with two 2 pF caps in series?

In theory, two 2 pF capacitors in series give 1 pF. In practice, this is almost never a good idea in RF circuits. You’re adding extra solder joints, more parasitic inductance, and more footprint area — all of which degrade performance at high frequency. If 1 pF isn’t available, it’s better to choose the closest available standard value (0.8 pF or 1.2 pF) and verify your circuit still works, rather than building a series combination.

What tolerance should I specify for a 1 pF capacitor in a matching network?

Use ±0.1 pF absolute tolerance. Percentage tolerances are meaningless at this capacitance value. ±0.25 pF is acceptable for less critical applications, but for anything where impedance accuracy matters — antenna matching, RF filter, oscillator load — stick to ±0.1 pF. The price difference between ±0.1 pF and looser tolerances is negligible in small quantities.

Does the PCB substrate matter when using 1 pF capacitors?

Yes, significantly. On standard FR4, the relatively high loss tangent (tanδ ≈ 0.02) and the dimensional variation of the substrate affect parasitic capacitance and insertion loss. High-frequency designs using 1 pF caps are often built on Rogers RO4350B or similar low-loss RF laminates where the electrical properties are tighter and the loss tangent is lower (tanδ ≈ 0.004). If you’re building on FR4 and seeing unexpected performance, parasitic effects from the substrate could be contributing.

Why does my 1 pF capacitor simulation not match measured results?

The most common cause is that your simulation doesn’t include PCB parasitics. A schematic-level SPICE simulation with an ideal 1 pF cap won’t account for the land pattern capacitance, trace inductance, or the capacitance of nearby vias. Use S-parameter models from the manufacturer (available from Murata SimSurfing, TDK, or Kemet KSIM) and consider running an EM simulation of the layout before relying on simulated results.

Working with 1 pF capacitors is one of those skills that separates RF engineers from general PCB designers. The component is simple — a small ceramic chip with two terminals — but getting it right requires understanding parasitics, dielectric selection, tolerance impact, and layout discipline. Get those right, and a 1 pF cap can make the difference between a matched antenna system and one that wastes half your transmit power in reflected losses.