“4.7uF as Standard LDO Output Capacitor,” “DC-DC Converter Applications,” “Audio Circuit Applications,” “PCB Layout Essentials” all used as section anchors

The 4.7uF capacitor appears on more reference schematics, evaluation boards, and production designs than almost any other passive component value at its size. Open almost any LDO datasheet, buck converter reference design, or microcontroller application note and you’ll find a 4.7µF specification at the output pin, often in parallel with a 100nF ceramic. It’s not an accident. The 4.7uF value sits in a precise engineering sweet spot — large enough to maintain regulator loop stability and handle load transients, small enough to avoid excessive inrush current and fit into compact SMD packages.

But picking any 4.7uF and calling it done is a fast path to field failures, oscillating regulators, and EMC pre-compliance surprises. This guide covers what the 4.7uF capacitor actually does in each application, which dielectric technology belongs where, and the PCB layout decisions that determine whether it performs as intended.

What Is a 4.7uF Capacitor? Value, Units, and Markings

Understanding the 4.7µF Designation

The notation 4.7uF (or 4.7µF) means 4.7 microfarads — 4.7 × 10⁻⁶ farads. It appears in several equivalent forms:

Notation	Equivalent	Where You’ll See It
4.7 µF	4,700 nF	Datasheets, schematics
4.7 uF	0.0000047 F	ASCII BOMs, PCB silkscreen
4700 nF	4,700,000 pF	Occasionally in RF/filter references
4.7 × 10⁻⁶ F	—	SPICE simulation netlists

When a regulator datasheet specifies a 4.7µF output capacitor and your supplier’s catalog lists “4700nF 16V X5R 0805,” those are the same component value. Getting this wrong wastes time and occasionally money.

How a 4.7uF Capacitor Is Marked

Electrolytic through-hole parts print the value and voltage directly on the sleeve — “4.7µF 50V” or “4.7uF 25V” — with a stripe identifying the negative lead. SMD electrolytic parts mark the top face similarly. SMD MLCC parts in 0805 and larger packages may carry a numeric code; in 0402 and 0603 packages there is typically no visible marking at all. This means a 4.7uF 0402 X5R cap and a 4.7uF 0402 X7R cap are visually indistinguishable once they leave the reel. Your BOM, placement files, and assembly traveler must carry this information unambiguously — it cannot be inferred from the board.

4.7uF Capacitor Types: Dielectrics, Performance, and Tradeoffs

Getting the dielectric type right for a 4.7uF capacitor is arguably more important than for smaller values, because this value is so often used in stability-critical LDO output applications where wrong dielectric selection produces oscillating regulators.

Aluminum Electrolytic

The classic through-hole choice for a 4.7uF at elevated voltages. A 4.7uF 50V radial electrolytic is inexpensive, has a well-understood ESR range (typically 1–10Ω at 120Hz), and has no DC bias capacitance loss. The weakness is high-frequency performance — above a few hundred kHz the electrolytic’s internal series inductance causes it to resonate and then behave inductively, making it ineffective at high-frequency noise filtering without a parallel ceramic cap. Aging is the other concern: the electrolyte slowly evaporates over time, increasing ESR and reducing effective capacitance. Budget industrial designs or anything running at ≤85°C with a 10-year lifespan target need to account for electrolytic aging in their reliability analysis.

Solid Tantalum

A 4.7uF solid tantalum in B or C case was historically the default LDO output capacitor on 3.3V and 5V rails. Tantalum’s ESR (typically 0.1–1Ω) is stable across temperature, it has no aging mechanism, and it retains its capacitance far better under DC bias than X5R/X7R ceramics. The ESR in this range was actually beneficial for older LDO topologies that required a minimum ESR on the output capacitor for loop stability. The risks: tantalum is polarized and catastrophically fails on reverse voltage, it cannot handle surge current at power-up, and it is significantly more expensive per unit than a ceramic equivalent. In modern designs where the regulator is ceramic-stable, tantalum at 4.7uF is increasingly hard to justify on cost alone.

X5R and X7R MLCC (The Modern Default)

For most new designs on 3.3V and 5V rails, a 4.7uF X5R or X7R MLCC in 0805 is the correct starting point. It offers the lowest ESR of any technology at this value (typically 5–50mΩ at high frequency), no polarity, no aging, small footprint, and the lowest cost per unit at production volumes. X7R operates to +125°C (versus +85°C for X5R) and is preferred for automotive and industrial temperature ranges.

The critical issue that bites engineers who don’t read beyond the headline spec: DC bias derating. A 4.7uF X7R rated at 10V on a 5V rail can lose 40–60% of its nominal capacitance — leaving you with roughly 1.9–2.8µF in circuit. This is directly how LDO oscillation field failures happen: the engineer specifies 4.7uF for stability margin, procurement substitutes a Z5U or cheap X7R on the minimum rated voltage, and the effective in-circuit capacitance drops below the minimum needed for loop stability.

A real-world account from engineering forums describes exactly this scenario: the circuit designer specifies 4.7uF, purchasing buys the cheapest part that “looks like 4.7uF/10V” using Z5U dielectric, the Z5U delivers approximately 2µF in circuit, and the LDO oscillates. The regulator gets blamed rather than the wrong capacitor dielectric.

The solution is straightforward: always specify 4.7uF X5R or X7R at a voltage rating 3× or more above your operating rail voltage. For a 3.3V rail, use a 4.7uF 16V X5R. For a 5V rail, use 4.7uF 25V X7R. The higher-voltage part retains 85–95% of its nominal capacitance under bias and costs only marginally more.

Polymer Electrolytic

Polymer aluminum or polymer tantalum capacitors at 4.7uF offer ESR approaching MLCC levels — often in the 10–50mΩ range — with much better capacitance stability under DC bias than X5R/X7R ceramics. They carry no piezoelectric microphony risk, making them useful on analog supply rails near precision amplifiers or PLLs where ceramic self-noise would be problematic. Their cost premium over MLCC makes them a targeted choice rather than a default, but for low-noise audio power supply design or RF front-end supply rails they are often the best engineering answer.

4.7uF Capacitor Technology Comparison

Type	ESR	Polarity	DC Bias Stability	Voltage Range	Aging	Best Application
Aluminum Electrolytic	1–10 Ω	Polarized	Good	6.3V–450V	Yes	Budget PSU, high-voltage output
Solid Tantalum	0.1–1 Ω	Polarized	Good	4V–50V	No	Legacy LDO output (ESR-critical)
X5R MLCC	5–50 mΩ	None	Poor (derate)	4V–50V	No	3.3V/5V LDO output (specify 16V+)
X7R MLCC	5–50 mΩ	None	Poor (derate)	4V–100V	No	Industrial/automotive LDO output
Polymer	10–50 mΩ	Polarized	Good	2.5V–25V	No	Analog/audio supply, low-noise RF

4.7uF Capacitor as the Standard LDO Output Capacitor

Why LDOs Specify 4.7uF

A low-dropout regulator maintains a stable output voltage by comparing its output through a feedback network to an internal reference and adjusting a pass element (typically a PMOS FET) in real time. This feedback loop has finite bandwidth. When the load suddenly demands more current — a microcontroller waking from sleep, an ADC starting a conversion, a transceiver enabling its RF stage — the LDO’s control loop cannot respond instantaneously. The output capacitor must supply this transient current while the loop catches up.

A minimum output capacitance is required not just for transient response but for loop stability. The output capacitor and its ESR contribute a pole-zero pair to the LDO’s open-loop transfer function. Without sufficient capacitance, the phase margin of the control loop falls below safe margins and the output voltage oscillates. A minimum capacitance of 1µF with a maximum ESR of 1Ω is a common minimum requirement — but most modern LDOs specify 4.7uF or 10uF at their outputs to provide adequate transient response headroom.

ESR Window: The Stability Band That Trips Up Engineers

Most modern ceramic-stable LDOs specify an ESR window for the output capacitor — a minimum AND a maximum ESR at the operating frequency. Too high an ESR degrades PSRR and allows more noise onto the output rail. Too low an ESR on older LDO topologies causes the control loop to become under-damped and oscillate.

The critical lesson: when using a 4.7uF MLCC on an LDO output, always verify the regulator datasheet’s stability region. Some older parts (including variants of the LM1117 family, the AP1117, and others with external compensation requirements) explicitly need 0.15Ω–0.5Ω minimum ESR on the output cap — a requirement that a modern MLCC at 5–20mΩ does not meet. For these parts, a 4.7uF solid tantalum or a 4.7uF polymer cap is the correct choice. For modern LDOs designed for ceramic output caps (TI’s TPS7A series, Analog Devices’ ADP151 family, most post-2015 LDO designs), the X5R or X7R MLCC is appropriate.

Transient Response: How 4.7uF Compares to Other Values

The output capacitor must supply current during a load transient before the LDO feedback loop can respond. The voltage droop during a load step is approximately:

ΔV ≈ ΔI × t_response / C_out

Where ΔI is the load current step, t_response is the LDO response time, and C_out is the output capacitance. For a 200mA load step with a 1µs LDO response time and 4.7µF output cap: ΔV ≈ 0.2 × 0.000001 / 0.0000047 ≈ 43 mV. With a 1µF output cap, the droop would be ~200mV — too large for many 3.3V logic supplies. With 10µF, it drops to ~20mV. The 4.7µF value positions the transient droop in a practical range for most moderate-current applications without requiring an excessively large capacitor.

Output Capacitance	Approx. Droop (200mA step, 1µs response)
1 µF	~200 mV
4.7 µF	~43 mV
10 µF	~20 mV
22 µF	~9 mV

This table explains why 4.7µF and 10µF both appear so commonly in LDO application circuits: the choice between them depends on the load current step magnitude and the system’s tolerance for output voltage droop during transients.

4.7uF Capacitor in DC-DC Converter Applications

Buck and Boost Converter Output Filtering

In switching regulators, the 4.7uF capacitor often appears at the converter output in combination with the main inductor to form the LC output filter. The output ripple voltage is:

ΔV_out ≈ ΔI_L / (8 × f_sw × C_out)

For a 500kHz switcher with 100mA inductor ripple and a 4.7µF output cap: ΔV_out ≈ 0.1 / (8 × 500,000 × 0.0000047) ≈ 5.3 mV, which is acceptable for most logic-level loads. A single 4.7µF X7R MLCC on the output of a 500kHz–2MHz synchronous buck converter is the most compact solution for low-current (<500mA) supply rails.

Input Capacitor Role in Switching Supplies

At the input of a DC-DC converter, a 4.7uF ceramic handles the high-frequency switching current ripple drawn from the input supply. The input capacitor must absorb the discontinuous inductor current switching at the converter’s frequency. A 4.7uF X7R rated at 25V on the input of a 12V→5V buck is a clean, compact solution for the input bypass — with the higher voltage rating ensuring minimal capacitance loss under the 12V DC bias.

4.7uF Capacitor in Audio Circuit Applications

Signal Coupling at Line Level

A 4.7uF capacitor in series with an audio signal path creates a high-pass filter with a cutoff frequency of f = 1 / (2π × R × C). With a 10kΩ load impedance: f = 1 / (2π × 10,000 × 0.0000047) ≈ 3.4 Hz — well below the audible range. The 4.7µF is thus an excellent coupling cap for line-level audio stages where DC blocking is needed without any LF attenuation in the audio band.

In speaker crossover networks, a 4.7uF non-polarized capacitor — either a bipolar electrolytic or a film type — sets the high-pass rolloff for a tweeter. In an 8Ω tweeter circuit, 4.7µF gives a first-order crossover at approximately f = 1 / (2π × 8 × 0.0000047) ≈ 4.2 kHz — a useful tweeter protection point. A 4.7uF non-polarized electrolytic at 100V is a standard component for this application, with a film type preferred where lower distortion matters.

Power Rail Decoupling in Audio Designs

In audio amplifier supply rails, the 4.7uF sits in the mid-tier of the decoupling hierarchy: larger than the 100nF local bypass but smaller than the bulk 47µF or 100µF electrolytic. It handles transient current demands in the few-hundred-kHz range where the main bulk caps have already hit series resonance.

PCB Layout Essentials for the 4.7uF Capacitor

Proper placement and routing of a capacitor on a PCB is as critical as the value and dielectric selection — especially for LDO output caps where impedance at the regulator feedback node directly affects stability.

LDO Output Cap Placement

Place the 4.7uF output capacitor as close as possible to the LDO output pin. The trace between the LDO output and the capacitor pad carries the feedback current that stabilizes the control loop — even a few nanohenries of parasitic inductance in this trace can affect phase margin at high frequencies. Use a short, wide trace directly from the output pin to the capacitor pad, then a low-impedance via to the ground plane from the capacitor’s ground pad.

For modern LDOs in small-outline packages, the ideal layout places the 4.7uF 0805 MLCC immediately adjacent to the output pin — within one pad-width if the package geometry allows — with a via-in-pad or close-via ground connection.

DC Bias Derating: The Practical Calculation for LDO Output Caps

Before finalizing a 4.7uF X5R or X7R MLCC on a voltage rail, calculate the effective in-circuit capacitance. Using a 4.7uF X5R 10V part on a 3.3V rail: at 33% of rated voltage, a typical X5R retains approximately 75–85% of its nominal capacitance, giving 3.5–4.0µF effective. If the LDO’s minimum stability capacitance is 4.7µF, this part is marginal. Specifying 4.7uF X5R at 16V on the same 3.3V rail pushes the bias ratio to 20%, retaining 90–95% capacitance — a safely comfortable 4.4–4.5µF effective.

Always use the manufacturer’s online simulation tool (Murata SimSurfing, TDK Product Selector, KEMET K-SIM) to check actual capacitance at operating voltage before issuing the BOM.

Package and Footprint Considerations

The 4.7uF capacitor is available in a wide range of SMD packages. Package choice affects both ESL and board-space usage:

Package	Nominal ESL	Typical Footprint	Use Case
0402	~0.3–0.5 nH	Very small	Space-critical 3.3V rails
0603	~0.5–0.8 nH	Compact	General digital supply bypass
0805	~0.8–1.5 nH	Standard	LDO output (most common)
1206	~1.0–2.0 nH	Larger	Higher capacitance retention at bias
Through-hole	~5–20 nH	Large pitch	Audio crossovers, prototyping

For LDO output duty on a 3.3V or 5V rail, 0805 X5R/X7R at 16V or 25V is the most practical choice — it balances capacitance retention, availability, assembly yield, and ESL.

Useful Resources for 4.7uF Capacitor Selection

• Murata SimSurfing: product.murata.com/en-global/tools/simsurfing — Model real impedance vs. frequency and DC bias derating for 4.7uF MLCCs; essential for LDO output stability verification
• KEMET K-SIM: ksim3.kemet.com — Spice model and impedance simulation for KEMET ceramic and polymer capacitors at specific bias voltages
• TDK Product Selector: product.tdk.com — Filter 4.7uF MLCCs by dielectric, voltage rating, and package with full datasheet and DC bias curves
• Analog Devices AN-1099: analog.com — Capacitor selection guidelines for LDO bypass including effective capacitance calculation at DC bias and temperature
• Infineon LDO Output Capacitor Selection Guide: community.infineon.com — Practical stability region analysis for X5R/X7R vs. tantalum on LDO outputs
• Digi-Key Parametric Search: digikey.com/capacitors — Cross-reference 4.7uF capacitors across dielectric, voltage, and package with live pricing and stock

Frequently Asked Questions About the 4.7uF Capacitor

Q1: Why do so many LDO datasheets specify a 4.7uF output capacitor? The 4.7µF value provides adequate phase margin for the LDO control loop while keeping the capacitor compact enough for SMD placement. It also gives sufficient charge storage to handle typical microcontroller and analog IC load transients without excessive output voltage droop. Larger values (10µF, 22µF) improve transient response further but increase cost and board area; smaller values (1µF, 2.2µF) may not meet minimum stability requirements under worst-case DC bias derating. The 4.7µF is the practical middle ground that most LDO control loop designs accommodate.

Q2: Can I use a 4.7uF Z5U ceramic capacitor as an LDO output cap? No — and this is a well-documented failure mode. A Z5U 4.7uF at its rated voltage delivers roughly 20% of nominal capacitance — approximately 0.9µF — which is well below the minimum for most LDO loop stability requirements. Z5U capacitors have terrible characteristics versus both temperature and DC voltage. They are effectively unsuitable for any supply rail application. Always specify X5R or X7R dielectric for 4.7uF bypass and output filter duty. Y5V is similarly unsuitable for the same reasons.

Q3: Is a 4.7uF MLCC better than a 4.7uF tantalum for LDO output? For modern LDOs specifically designed for ceramic output capacitors (most designs after ~2010), the X5R or X7R MLCC is better: lower cost, no polarity risk, no aging, and smaller footprint. For older LDO designs that require a minimum ESR of 0.1–0.5Ω for stability (LM1117 variants, AP1117, certain legacy industrial regulators), a 4.7uF solid tantalum or polymer capacitor is the correct choice because the MLCC’s sub-50mΩ ESR may cause the control loop to become under-damped and oscillate. Always check the datasheet stability region chart before deciding.

Q4: What voltage rating should I specify for a 4.7uF X7R MLCC on a 3.3V rail? At minimum 10V, but 16V is strongly preferred and 25V is better still. The reason: a 4.7uF X7R rated at 10V on a 3.3V rail operates at 33% of rated voltage. Depending on the specific part, this results in roughly 60–80% capacitance retention — leaving you with ~2.8–3.8µF effective. A 16V-rated X7R on 3.3V operates at only 20% of its rated voltage, retaining 85–95% of capacitance and giving a safe 4.0–4.5µF effective. The 16V part is typically the same size and costs only fractionally more than the 10V version, making it an obvious engineering choice.

Q5: Can I substitute a 4.7uF capacitor with a 10uF if I only have 10uF parts available? In most power supply bypass and LDO output applications, yes — a 10µF will work and will actually improve transient response compared to the original 4.7µF. The exceptions are: circuits where the capacitor forms an RC timing network where the exact value is critical, speaker crossover networks where the crossover frequency is defined by the capacitor value, and very specific LDO designs that specify a maximum output capacitance for stability reasons (rare in modern devices, but worth checking in the datasheet). For all standard supply rail bypass and LDO output applications, going higher in capacitance is safe and often beneficial.

The 4.7uF capacitor doesn’t get the attention it deserves in most design reviews — it’s treated as a default entry on the BOM rather than an engineered choice. But regulator stability, transient response, audio frequency response, and switching converter ripple all depend on having the right capacitor at this value. Specify the dielectric correctly, account for DC bias derating in your effective capacitance calculation, and route the output cap tight to the regulator pin — and a component that costs a few cents will earn its place in every board you ship.