The 4700uF capacitor is the backbone of high-current PSU filtering. Learn ripple calculations, ESR specs, voltage derating, layout tips, and top manufacturer comparisons.
When a power supply needs to deliver serious current — think 5A, 10A, 20A and beyond — the filter capacitor can no longer be an afterthought. At that scale, a 4700uF capacitor becomes a real engineering decision. This is the component sitting between your rectifier and your load, absorbing ripple, bridging transients, and keeping your rail from collapsing when the load suddenly demands more current than the transformer can instantly deliver. If you’ve ever scoped a 5V rail and watched it sag 500mV under a step load, you already understand exactly why this value exists.
Why 4700 µF? Understanding the Reservoir Capacitor Concept
The term “reservoir capacitor” is more descriptive than “filter capacitor” — it implies exactly what this component does. It stores charge during the peaks of the rectified waveform and releases it during the valleys. The larger the reservoir, the smaller the ripple and the more energy is available during high-demand transients.
The 4700uF capacitor sits at roughly ten times the capacitance of the 470 µF workhorses used in moderate-current designs. That extra capacitance is not free — the component is physically larger, more expensive, and requires more careful placement — but for high-current applications, it’s often the difference between a stable power rail and a supply that falls apart the moment a motor spins up or a processor hits a computational peak.
Where Does 4700 µF Come From?
This is not an arbitrary value. Capacitor values follow the E6 or E3 preferred number series, and 4700 µF (often written 4.7 mF) is the standard step above 3300 µF and below 6800 µF. In practice, engineers often end up at 4700 µF either because the ripple calculation demands it or because paralleling two 2200 µF caps gives them 4400 µF and they round up to a single 4700 µF unit instead.
Ripple Voltage Calculation with a 4700 µF Capacitor
The fundamental formula governing ripple across a reservoir capacitor is:
V_ripple ≈ I_load / (f × C)
Where:
- I_load = DC load current (A)
- f = ripple frequency in Hz — 100 Hz for full-wave from 50 Hz mains, 120 Hz from 60 Hz mains
- C = capacitance in farads (0.0047 F for 4700 µF)
Let’s run some real numbers:
| Load Current | Ripple Freq | Capacitance | Estimated Ripple (Vpp) |
| 1 A | 100 Hz | 4700 µF | 2.13 V |
| 2 A | 100 Hz | 4700 µF | 4.26 V |
| 5 A | 100 Hz | 4700 µF | 10.6 V |
| 5 A | 120 Hz | 4700 µF | 8.83 V |
| 10 A | 100 Hz | 4700 µF | 21.3 V |
At 10A loads, a single 4700uF cap is nowhere near enough — you’d parallel several or step up to 10,000 µF and beyond. But for 1–3A loads, 4700 µF delivers ripple levels that a downstream linear regulator or error amplifier can comfortably handle.
Key Specifications of a 4700 µF Capacitor
Datasheet values are where real engineering decisions happen. Here are the parameters that actually matter when selecting a 4700uF capacitor for a power supply design:
| Parameter | Typical Range | Engineering Notes |
| Capacitance | 4700 µF ±20% | Standard electrolytic tolerance |
| Voltage Rating | 6.3V – 100V | Most common: 16V, 25V, 35V, 50V |
| ESR (at 100 Hz, 20°C) | 0.02 – 0.8 Ω | Lower is better; critical for ripple current |
| Ripple Current (105°C) | 1.5 – 6.0 A RMS | Derate heavily at elevated temperatures |
| Leakage Current | ≤ 0.03 × C × V (µA) | Higher at elevated temp and voltage |
| Operating Temperature | –40°C to +85°C or +105°C | Always specify 105°C for PSU duty |
| Endurance (at rated temp) | 1,000 – 10,000 hours | Lifetime at continuous rated conditions |
| Physical Size (radial) | Ø12.5mm–Ø22mm × 20–40mm | Voltage rating drives size significantly |
| Capacitance at –40°C | ~60–70% of nominal | Cold performance derate matters in automotive |
Voltage Rating and Derating: Don’t Skimp Here
A 4700uF capacitor on a 24V rail needs a minimum 35V rating, and ideally 50V for a 20% safety margin. The dielectric in an aluminum electrolytic degrades faster when operated close to its rated voltage — accelerating dry-out, increasing leakage, and shortening service life dramatically. The additional cost of stepping from a 35V to a 50V part is usually cents. The cost of a field failure is not.
ESR: The Hidden Performance Killer
Equivalent Series Resistance directly adds to your output ripple voltage through a second ripple component:
V_ESR = I_ripple × ESR
A 4700uF cap with 0.4 Ω ESR carrying 3A of ripple current adds 1.2V of ripple that your capacitance calculation didn’t account for. For switching supplies operating at higher frequencies, ESR becomes even more dominant because capacitive reactance drops but ESR stays roughly constant. Low-ESR or polymer variants are the right choice for any SMPS output stage.
Common Applications of the 4700uF Capacitor
Linear Power Supply Output Filtering
This is the original home of large electrolytic capacitors. In a classic unregulated linear supply — transformer, bridge rectifier, capacitor — the 4700uF cap is the main reservoir doing all the heavy lifting before regulation. Post-regulator, a smaller cap handles high-frequency noise.
For a 5V, 3A linear supply from 50 Hz mains, the 4700uF value keeps ripple under 2V at the regulator input, well within the dropout headroom of a 78xx or LM317 series device.
Audio Amplifier Power Rails
High-power class-AB amplifiers are notoriously current-hungry during low-frequency musical content. Bass transients can demand 5–15A for milliseconds. Large reservoir capacitors — often 4700uF in pairs on positive and negative rails — absorb these transients and prevent rail sag that would otherwise compress and distort the audio.
This is why audiophiles fetishize large power supply caps: they’re not wrong. A stiffer power rail genuinely reduces intermodulation distortion caused by power supply modulation.
Industrial Motor Drive PSUs
VFDs and servo drives need substantial bulk capacitance on the DC bus to handle regenerative braking energy and absorb switching transients from the inverter stage. 4700uF capacitors at 200–400V ratings appear frequently in the DC link section of industrial drives.
Embedded System and SBC Power Rails
Single-board computers, especially those running high-performance SoCs, can draw surge currents of 5–10A during boot or heavy computation. A 4700uF cap placed close to the main power input connector on the PCB provides hold-up energy during these transients and prevents the upstream supply from drooping the rail below the processor’s minimum operating voltage.
Server and Telecom Power Distribution
48V telecom bus systems and server PSU outputs frequently use 4700uF bulk capacitors at the point-of-load to decouple the downstream DC/DC converters from one another and to provide local hold-up during redundant supply switchover events.
PCB Layout and Placement Guidelines
A capacitor on a PCB is only as effective as its physical placement and the quality of the copper connecting it to the circuit. This is especially true for large electrolytics where parasitic inductance can significantly impair high-frequency filtering performance.
For a 4700uF through-hole electrolytic:
Keep lead length minimal. Every millimeter of lead adds inductance. Trim leads to the shortest practical length before soldering. Target under 3mm above the PCB surface.
Use wide, direct copper pours. Don’t route a thin trace from the capacitor to the rail. Pour copper on both layers if necessary and use vias to stitch them together for high-current paths.
Place it close to the source. Position the reservoir cap as close to the rectifier output or regulator input as the layout allows. Distance equals inductance, and inductance defeats filtering at higher frequencies.
Mind the thermal environment. Aluminum electrolytics have a finite life that halves for every 10°C rise above rated temperature. Keep 4700uF caps away from heat sinks, power transistors, and other hot components. If airflow is limited, derate the ripple current rating accordingly.
Popular 4700 µF Capacitor Series and Manufacturers
| Series | Manufacturer | Voltage Options | ESR (typ.) | Ripple Current | Temp / Lifetime |
| EEU-FM / EEU-FP | Panasonic | 6.3–50V | 0.04–0.3 Ω | 2.1–5.3 A | 105°C / 2000 hr |
| UHW / UKW | Nichicon | 16–63V | 0.03–0.25 Ω | 2.5–6.0 A | 105°C / 3000 hr |
| LGX / LGU | KEMET | 10–63V | 0.05–0.35 Ω | 2.0–5.0 A | 105°C / 2000 hr |
| 860-Series | Würth Elektronik | 16–63V | 0.04–0.28 Ω | 1.8–4.5 A | 105°C / 2000 hr |
| RJC / RJH (Polymer) | Nichicon | 6.3–16V | < 0.012 Ω | 5.0–9.0 A | 105°C / 2000 hr |
| EEHZG (Polymer) | Panasonic | 6.3–16V | < 0.010 Ω | 5.5–10.0 A | 105°C / 5000 hr |
Polymer types have dramatically lower ESR and longer lifetimes but are currently limited to lower voltage ratings. For 48V and above, standard aluminum electrolytics with low-ESR ratings remain the practical choice.
Useful Resources for Engineers Working with 4700 µF Capacitors
Panasonic Capacitor Product Search — https://industrial.panasonic.com/ww/products/capacitors Full parametric search across FM, FP, and polymer series with datasheet downloads.
Nichicon Product Lineup — https://www.nichicon.co.jp/english/products/ UHW and UKW high-ripple series datasheets and application notes.
KEMET Capacitor Selector Tool — https://www.kemet.com/en/us/capacitors.html Includes SPICE models for simulation and ripple current calculators.
Würth Elektronik REDEXPERT — https://www.we-online.com/en/tools/redexpert Frequency-dependent impedance modeling; shows actual impedance curves across frequency.
Murata SimSurfing — https://ds.murata.co.jp/simsurfing/ Impedance simulation for capacitors across a wide frequency range.
IEC 60384-4 — Standard covering fixed aluminum electrolytic capacitors for electronic equipment. Essential reading for anyone writing procurement or qualification specifications.
5 FAQs About the 4700uF Capacitor
Q1: Can I parallel two 2200uF capacitors instead of using one 4700uF? Yes, and there’s actually an advantage to doing so — paralleling caps halves the effective ESR. Two 2200uF caps (total 4400uF) with 0.2Ω each gives you 0.1Ω combined ESR, which outperforms many single 4700uF parts. The trade-off is more board space and two mounting footprints. For high-ripple-current applications, paralleling is often the smarter choice.
Q2: What happens if I use a 4700uF cap with an insufficient voltage rating? Initially, very little. Over time, the dielectric breaks down, leakage current increases, and the capacitor fails — sometimes suddenly with venting, leakage of electrolyte, or an internal short. In worst cases this can damage surrounding components. Always respect voltage derating: use a cap rated at least 1.5× your operating voltage, preferably 2×.
Q3: How do I check if a 4700uF capacitor is failing in circuit? Use an in-circuit ESR meter — this is the single most useful diagnostic tool for electrolytic capacitors. A healthy 4700uF cap might measure 0.1–0.3Ω ESR. A failing cap can measure 1–10Ω or more. Visual inspection for bulging vents or electrolyte leakage around the base also catches obvious failures, but ESR measurement catches degraded-but-not-yet-failed caps that visual inspection misses entirely.
Q4: Do 4700uF capacitors have a shelf life? Yes. Aluminum electrolytics should ideally be re-formed if stored unused for more than two years. The oxide dielectric layer partially degrades without voltage applied to it. Re-forming involves slowly ramping up voltage while limiting current, allowing the dielectric to rebuild. Most manufacturers publish a re-forming procedure in their application notes. For production, FIFO stock management matters.
Q5: Is a 4700uF polymer capacitor better than aluminum electrolytic for SMPS output? For low-voltage rails (under 25V), polymer is almost always better: lower ESR means less output ripple for the same capacitance value, longer service life, and no risk of electrolyte dry-out. The drawback is higher cost and lower maximum voltage. For rails above 25V, the polymer options thin out quickly and aluminum electrolytic remains the standard. Many modern designs combine a large aluminum electrolytic for bulk capacitance with a smaller polymer cap in parallel for low-ESR high-frequency filtering.
Final Thoughts
A 4700uF capacitor is not a glamorous component. It sits quietly on the board, does its job, and is completely invisible when it’s working correctly. The only time it commands attention is when it fails — or when someone skimped on the spec and the power rail can’t hold up under load. Choose 105°C rated parts, respect the voltage derating rules, check the ESR and ripple current ratings against your actual operating conditions, and place it properly on the PCB. Do that, and this big aluminum cylinder will reliably protect your circuit for the lifetime of the product.
