1N4004G Rectifier Diode: Specifications, Polarity and Applications

The 1N4004G is a 400 V, 1 A general-purpose rectifier diode. Learn its ratings, derating and when a fast-recovery or Schottky part is the better choice.

Request a Quote

1N4004G Rectifier Diode: Specifications, Polarity and Applications

The Good-Ark 1N4004G diode is a standard silicon rectifier in the 1N4001G–1N4007G family. The reviewed datasheet lists 400 V repetitive peak reverse voltage and 1 A average rectified current in a DO-41 axial package. It is a candidate for suitable low-frequency rectification and other defined diode paths, but these ratings do not establish unrestricted mains use, fast-switching performance or 1 A operation under any mounting conditions.

For a replacement or new design, identify the manufacturer first, then check polarity, voltage exposure, current waveform and temperature. Similar base numbers appear in several catalogs, and suffix conventions are not universal. This guide uses Good-Ark’s official document for its model-specific statements and clearly labels application calculations as examples.

Last updated: October 16, 2026

What do the 400 V and 1 A ratings mean?

They describe different operating directions and conditions. The 400 V figure is repetitive reverse blocking capability, not the voltage dropped while conducting. The 1 A figure concerns average rectified forward current under the document’s conditions. Peak charging pulses and installed heat can impose additional constraints even if average load current looks acceptable.

Good-Ark family item	Reviewed value	Interpretation
1N4004G VRRM	400 V	Check actual reverse terminal stress
Average forward current	1 A	Read mounting and derating together
Package	DO-41 / DO-204AL	Check outline and lead arrangement
Listed forward-drop point	1.10 V at 1 A	Not a constant drop at every current

These entries come from the Good-Ark 1N400xG Rev. B datasheet. Preserve the exact conditions when comparing another manufacturer’s part. A higher reverse-voltage class does not independently improve current handling, cooling or circuit behavior. The rectifier selection guide explains why a voltage-and-current shortlist still needs a waveform review.

How do you identify anode and cathode?

The cathode is identified by the applicable band marking. Conventional forward current flows from anode to cathode when the circuit forward-biases the junction. The bar in the diode symbol represents the cathode, giving a way to connect the physical marking with the schematic. Confirm the actual product marking rather than relying on the direction of the printed part number.

On a board, read the circuit and the footprint indication together. Copying the orientation of an old component can preserve a previous assembly error. Where the mark is damaged or obscured, identify the part and connections before applying power. Lead length is not a reliable substitute for the documented polarity marking.

In a bridge, four diode orientations cooperate to maintain one output polarity. Understanding a single band is useful, but it does not by itself identify the bridge’s positive, negative and AC nodes. Review the complete connection. An axial diode installed backwards can change conduction or load the source in an unintended way, depending on the surrounding circuit.

1N4004G: identify the cathode band: Package concept only; verify the exact manufacturer drawing. — Original polarity illustration, not a dimensional package drawing.

Is 400 V enough for a mains-related circuit?

The complete reverse-voltage envelope decides. An ideal 230 V RMS sine wave peaks at approximately 325 V. At a hypothetical 253 V RMS high-line condition, the peak is about 358 V. Neither number includes relevant transients or every topology-dependent stress. A nominal 400 V diode therefore needs a justified application review, not a recommendation based on the nominal line alone.

Some circuits place the rectifier behind a transformer or other isolation and conditioning, creating a very different exposure. Others use capacitor or center-tapped connections whose reverse stress differs from a bridge. Measure or model the diode terminals under the required source and load states before choosing a voltage class.

These figures illustrate voltage comparison; they are not instructions to build a mains circuit. Work on mains-connected equipment requires its appropriate isolation, discharge and service procedures. A larger blocking number also does not resolve clearance, surge coordination or the limits of other components. The application-specific rectifier guide shows how the same role-first method changes with a vehicle environment.

Standard recovery does not mean a universal frequency limit

Commutation performance needs the actual switching conditions. The reviewed Good-Ark sheet includes a typical recovery time of 1 µs at IF = 0.5 A, IR = 1 A and recovery endpoint IRR = 0.25 A. That is a defined test result, not a guarantee that every circuit can switch at a frequency obtained by taking its reciprocal.

Recovery current, voltage, temperature and layout influence the installed event. A rectifier at a low-frequency input and one at a rapidly commutated converter output can have different duties inside the same power supply. The label “used in an SMPS” does not identify which requirement applies.

If recovery is important, compare supported dynamic data or select a suitable fast-recovery or Schottky candidate. The fast-recovery diode explanation covers those mechanisms. Avoid a blanket rule that 1N4004G is always suitable below one frequency and unsuitable above it; evaluate the required event, losses and protection behavior instead.

Current and heat: an illustrative operating check

Forward voltage multiplied by conducting current estimates dissipation. For an illustrative constant 0.6 A and assumed 0.9 V drop at that condition, the loss is about 0.54 W. A pair of similar conducting junctions in a constant-current bridge path contributes about 1.08 W together. These assumptions are not measured Good-Ark data, and a capacitor-input waveform needs a different time-average calculation.

Suppose an applicable installed thermal model gives 50 °C/W from junction to a defined reference. The single diode’s simplified rise would be 0.54 × 50 = 27 °C above that reference. The model must correspond to the board, leads and surroundings; copying an unrelated thermal resistance would make the arithmetic look precise without making the estimate valid.

Check the hottest required condition, including enclosure temperature and nearby heat. Review how the datasheet’s lead and ambient assumptions compare with the actual mounting. Nexperia’s thermal-parameter discussion explains why reference points and test boards matter. A surface reading and a current label are not a complete junction-temperature assessment.

Surge current is a separate application check

Startup can impose a different waveform from normal load. A discharged smoothing capacitor may draw a high charging pulse limited by the source and current path. Determine the capacitor state, source impedance, switching condition and credible repetition. A single-pulse rating does not establish unlimited repeated startup capability.

Do not use a surge figure as a continuous-current allowance. Pulse duration, shape and initial temperature matter, as do tracks, transformer windings, connectors and other devices in the path. If inrush controls are present, include their actual behavior in the model rather than assuming the capacitor always starts fully discharged or fully charged.

A replacement that survives one bench power-on has not necessarily covered a hot restart or the worst source condition. Retain the relevant startup record with the operating-current assessment. When failures cluster around switching on, investigate that event before deciding that a larger reverse-voltage suffix alone is the remedy.

From circuit current to temperature: Use the waveform and installed heat path, not the current label alone. — The forward-loss calculation uses assumed operating values; additional losses and thermal conditions remain separate.

1N4004G vs 1N4007G: what changes in the comparison?

The reviewed family assigns different reverse-voltage classes. It lists 1N4004G at 400 V and 1N4007G at 1000 V. Sharing the family and headline average-current class is useful for a first shortlist, but it does not prove every parameter identical or every substitution approved. Match the exact manufacturer and supporting document.

For a circuit whose missing requirement is reverse capability, a higher-voltage candidate may deserve evaluation. If the problem is charging-pulse heat or rapid commutation, the voltage increase alone may do little. Compare the package, forward behavior, dynamic data and required qualification as well as reverse rating.

The 1N4001G guide focuses on the low-voltage end of the family and transformer/capacitor stress. For ordering, use the part-specific sourcing workflow. Keep manufacturer and full code in the record rather than accepting a cross-reference as proof of interchangeability.

What can a diode-mode test tell you?

A meter can screen for a gross junction fault. After removing power and following the equipment’s isolation and discharge procedure, an appropriate test can reveal forward conduction and reverse blocking at the meter’s conditions. A low reading in both directions can indicate a short, but a parallel board path can produce a similar observation.

An open indication in both directions can reflect a damaged junction, poor probe contact or another limitation. Capacitors and surrounding circuitry can also make an in-circuit reading change over time. Resolve those influences before deciding that the component is defective. Where isolation is needed, use the service method appropriate to the equipment.

Ordinary diode mode does not exercise a 400 V blocking condition, high-current heating or reverse recovery. Passing it therefore does not prove fitness for reuse after overheating or a surge. Also investigate why the original part failed: an upstream fault or wrong operating condition can damage the replacement in the same way.

Keep a defensible application record

Write down the circuit role, voltage envelope, current waveform and mounting used to accept the candidate. Retain the exact datasheet and replacement comparison. This connects the diode’s familiar part number to the conditions that matter and makes later service or procurement decisions more reliable than a larger rating or a normal meter reading alone.

Use the 1N4004G ratings in the actual circuit

This page owns the 1N4004G voltage grade, polarity, operating checks, and family comparison. The rectifier operation guide explains how the current paths produce DC. Keep repeated-peak voltage, charging current, and the thermal boundary condition together when applying the device.

Frequently asked questions

Does the G suffix always mean lead-free?

No universal suffix meaning should be assumed across manufacturers. The reviewed Good-Ark document describes a glass-passivated rectifier family, while other manufacturers can use suffixes for different ordering or environmental conventions. Obtain the exact product and packaging documentation if materials compliance matters. A similar base number or one letter on the body is insufficient evidence of construction, certification or interchangeability. Keep those requirements separate from the electrical voltage and current comparison.

Can a 1N4007G replace a 1N4004G?

It is a candidate to evaluate, particularly when a higher reverse-voltage class is needed. Check manufacturer, package, forward behavior, dynamic requirements and any applicable approval criteria. A higher blocking rating does not cure excessive current pulses, poor cooling or an unsupported switching role. Retain the comparison and validate the conditions that governed the original selection. Cross-reference entries can identify options, but they do not independently approve the substitute in the actual circuit.

Is 1N4004G suitable for every 230 V application?

No. The nominal RMS input is only one starting value. Determine the relevant high-line peak, topology-dependent reverse stress and transients, then compare them with the exact diode’s capability and justified margin. Other parts and the equipment’s safety construction also impose limits. A 400 V rating does not certify a mains circuit or make all connections equivalent. Use the application’s design and service requirements rather than a generic part-number recommendation.

Can I use it as a relay flyback diode?

Only if its current, voltage, thermal and dynamic behavior meet that coil circuit’s requirements. A simple diode clamp can prolong current decay and change relay release time, so it is not always interchangeable with a higher-voltage clamp arrangement. Check the controller’s permitted stress and the required mechanical response. The coil current and repetition govern the energy flow; a familiar rectifier number alone does not establish compatibility with every relay or solenoid.

Why is a 1N4004G warm below 1 A?

Forward conduction still dissipates power, and the installed heat path may differ from the datasheet conditions. Pulsed charging can also create stresses not represented by the DC load value. Check the actual waveform, local temperature and mounting rather than assuming that any current below the headline rating guarantees cool operation. A correct thermal estimate needs a matching reference path. If heating is unexpected, investigate the circuit state and source before changing only the voltage class.

Does a normal meter reading prove the rectifier is good?

It proves only the observed low-current behavior under that test. It does not establish leakage at working voltage, pulse survival, hot performance or recovery behavior. In-circuit paths may hide faults or imitate a short. Follow the equipment’s isolation procedure and interpret both directions with the surrounding circuit in mind. A part that has overheated or suffered a surge can need application-relevant checks even when its ordinary diode-mode reading looks normal.

Continue through this engineering topic

For the complete selection, design, verification, and troubleshooting path, explore the Rectifier Selection and Ratings.