Learn how a 470uF capacitor works in PSU filtering and ripple reduction. Covers key specs, ESR, voltage derating, SMPS vs linear regulator use, manufacturer comparison tables, and PCB placement tips for engineers.
If you’ve spent any time debugging a noisy power rail or tracing an unstable supply rail on an oscilloscope, you already know how much a single well-chosen 470uF capacitor can change everything. This value sits in a sweet spot — large enough to handle meaningful bulk decoupling and ripple smoothing, small enough to be practical in tight board layouts. Let’s break down exactly what makes this component tick, where it earns its place, and how to spec it correctly for your next design.
What Is a 470 µF Capacitor and Why Does This Value Matter?
A 470uF capacitor stores 470 microfarads of charge — roughly in the middle of the electrolytic range used for power supply work. It isn’t the smallest (that’s your 10–100 µF decoupling caps) and it isn’t the largest bulk storage cap you’ll find in a PSU (those go into the thousands of µF). What it is, however, is a reliable workhorse value stocked by every major distributor and manufactured to tight tolerances by dozens of vendors.
From a PCB design perspective, 470 µF is often the first value engineers reach for when they need to filter a rectified DC rail in a linear supply, smooth the output of a switching converter, or hold up a voltage rail during brief load transients. Its capacitance is substantial enough to deliver real low-frequency filtering without demanding excessive board real estate.
How the 470 µF Capacitor Works in PSU Filtering
The Basic Ripple Problem
When AC mains power is rectified — either half-wave or full-wave — what you get on the DC side is not a clean flat line. It’s a pulsating waveform riding the DC average. This AC variation riding on top of your DC supply is called ripple voltage, and it causes noise, instability, and in audio or analog circuits, audible hum.
The capacitor’s job is to charge up during the peaks of the rectified waveform and discharge into the load during the valleys, effectively “filling in” the gaps and smoothing the output.
Ripple Reduction Formula
The peak-to-peak ripple voltage across a filter capacitor can be estimated with:
V_ripple ≈ I_load / (f × C)
Where:
- I_load = load current in amps
- f = ripple frequency in Hz (100 Hz for full-wave rectification from 50 Hz mains, 120 Hz from 60 Hz)
- C = capacitance in farads
Plugging in a 470uF capacitor (0.00047 F) with a 100 mA load at 100 Hz:
V_ripple ≈ 0.1 / (100 × 0.00047) ≈ 2.1 V peak-to-peak
Increase to 1 A load and that ripple jumps to 21 V — which is why large PSUs use multiple capacitors in parallel, or step up to 1000 µF and beyond. But for moderate loads, 470 µF is often exactly right.
Key Specifications of a 470 µF Capacitor
When you pull a 470uF capacitor from a datasheet, these are the numbers that actually matter in real circuit design:
| Parameter | Typical Range | Notes |
| Capacitance | 470 µF ±20% | Most electrolytics are ±20% tolerance |
| Voltage Rating | 6.3V – 450V | Match to your rail with margin |
| ESR (Equivalent Series Resistance) | 0.02 – 2 Ω | Critical for ripple current handling |
| Ripple Current Rating | 0.5 – 3 A RMS | Derate for temperature |
| Temperature Range | –40°C to +105°C | 105°C grades preferred for PSU use |
| Leakage Current | < 0.01 × C × V | Increases with age and temperature |
| Lifetime | 1,000 – 10,000 hrs at rated temp | Key reliability parameter |
| Package (Radial Through-Hole) | Ø6.3mm – Ø16mm × 11–25mm | Size varies with voltage rating |
| Package (SMD Polymer) | D, E, V case sizes | Lower ESR, more expensive |
Voltage Rating: Always Derate
Never run a capacitor at its rated voltage. Standard practice is to derate by at least 20%, and many engineers use 50% derating in harsh or high-reliability designs. A 25V-rated 470uF cap on a 12V rail? Comfortable. A 16V-rated part on a 12V rail? Too tight — even a small transient can stress the dielectric.
ESR Is Not Optional Information
Low ESR is critical in switching power supply output stages. High ESR means more of the ripple current turns into heat inside the capacitor rather than being filtered. It also adds directly to your output ripple voltage:
V_ESR_ripple = I_ripple × ESR
For a 1A ripple current through a 470uF cap with 0.5 Ω ESR, that’s an additional 0.5 V of ripple you hadn’t planned for. Polymer electrolytic or OS-CON type capacitors offer ESR values an order of magnitude lower than standard aluminum electrolytics.
Common Applications of the 470uF Capacitor
Output Filtering in Linear Regulators
Linear regulators like the LM317 or 7805 series typically recommend a 0.1 µF ceramic on the output for high-frequency stability and a larger electrolytic — often 470uF — for bulk filtering and load transient response. Without the 470uF, the output may ring or sag during sudden load steps.
Bulk Decoupling in SMPS Designs
In flyback, buck, and boost converters, the output capacitor is responsible for both filtering the switching frequency ripple and supplying instantaneous current during load transients. The 470uF value appears frequently in 12V and 5V SMPS outputs for loads up to a few amps.
Audio Amplifier Power Rails
In class-AB amplifier PSUs, 470uF capacitors are used in pairs (for positive and negative rails) at the secondary side of the transformer. Larger values improve bass performance by reducing rail sag during high-current audio peaks.
Motor Driver Hold-Up Capacitance
On motor control boards, 470uF capacitors are placed close to the H-bridge or driver IC to absorb the current spikes that occur during PWM switching and motor commutation events.
PCB Design Considerations
Placement matters enormously. A capacitor on a PCB should be placed as close as possible to the IC or circuit it’s filtering — not on the other side of the board where trace inductance defeats its purpose. For through-hole electrolytics, keep the lead length short. The parasitic inductance of even a few centimeters of trace begins to limit filtering effectiveness above a few kHz.
470 µF Capacitor Specifications Comparison Table
| Series | Manufacturer | Voltage | ESR (100 Hz) | Ripple Current | Temp Rating | Use Case |
| EEU-FM Series | Panasonic | 6.3–100V | 0.06–0.3 Ω | 0.9–2.1 A | 105°C | General PSU |
| UHW Series | Nichicon | 16–100V | 0.05–0.2 Ω | 1.0–2.5 A | 105°C | High ripple SMPS |
| 860010672013 | Würth | 25–63V | 0.08–0.25 Ω | 0.8–1.8 A | 105°C | Industrial |
| EEHZK Series | Panasonic (Polymer) | 4–16V | < 0.018 Ω | 2.5–4.0 A | 105°C | Low ESR SMPS |
| UCS Series | Nichicon (Polymer) | 6.3–16V | < 0.015 Ω | 3.0–5.0 A | 105°C | High-frequency SMPS |
Useful Resources for Engineers
Here are some genuinely useful references when working with 470uF capacitors:
- Murata SimSurfing (https://ds.murata.co.jp/simsurfing/) — Impedance simulation tool for capacitors across frequency
- Panasonic Capacitor Selector (https://industrial.panasonic.com/ww/products/capacitors) — Full series datasheets and parametric search
- Nichicon Capacitor Products (https://www.nichicon.co.jp/english/products/) — UHW, UHE, and polymer series datasheets
- KEMET Spice Models (https://www.kemet.com/en/us/capacitors.html) — Downloadable SPICE models for simulation
- Würth Elektronik REDEXPERT (https://www.we-online.com/en/tools/redexpert) — Frequency-dependent impedance and ESR modeling
- IPC-A-610 — Acceptability of Electronic Assemblies standard, covers capacitor mounting inspection criteria
5 Frequently Asked Questions About the 470 µF Capacitor
Q1: Can I replace a 470uF capacitor with a higher value, like 1000uF? In most cases, yes — more capacitance generally means less ripple and better transient response. The exception is certain linear regulators that specify a maximum output capacitance due to stability concerns. Always check the datasheet of the driving IC before upsizing.
Q2: What voltage rating should I choose for a 12V supply? A 25V-rated 470uF cap gives you a comfortable 2× derating margin on a 12V rail. For higher reliability or industrial applications, a 35V rating is even safer and often the same price.
Q3: My 470uF capacitor is getting warm during operation — is that normal? Some warmth is normal due to ripple current flowing through ESR. Excessive heat (too hot to touch) indicates either the ripple current exceeds the cap’s rating, the ESR is too high, or the ambient temperature is too high. Measure the ripple current and compare to the datasheet rating.
Q4: How do I identify a failed 470uF electrolytic capacitor on a PCB? Physical signs include a bulging top vent, electrolyte leakage (brown or dried crust around the base), and in-circuit ESR measurement significantly above the datasheet value. An LCR meter or dedicated ESR meter is the most reliable diagnostic tool.
Q5: What’s the difference between a standard aluminum electrolytic and a polymer 470uF cap? Polymer capacitors use a conductive polymer electrolyte instead of liquid electrolyte. This gives them 5–20× lower ESR, much longer operating lifetime (especially at high temperatures), and immunity to dry-out failure. They cost more but are the right choice for high-frequency SMPS output filtering.
Final Thoughts
The 470uF capacitor is one of those components that doesn’t get much attention until something goes wrong — and when you’ve watched a power supply rail collapse under load because someone specified an undersized or poor-quality filter cap, you learn quickly to take it seriously. Spec for voltage with margin, pay attention to ESR and ripple current ratings, choose 105°C parts for any PSU application, and place them properly on the PCB. Do those things and this humble capacitor will quietly do its job for the lifetime of your product.
