What Is a 1F4G Fast Recovery Rectifier?

by

The 1F4G is a 1 A, 400 V glass-passivated fast recovery rectifier diode in an R-1 axial package. Its 150 ns maximum reverse recovery time, 1.3 V maximum forward drop, 30 A surge capability, and low leakage suit compact power supplies, battery chargers, freewheeling paths, and switching circuits requiring faster turn-off than a standard rectifier can reliably provide in practice.

(Last modified date: August 31, 2026)

Key Takeaways

  • The 1F4G fast recovery rectifier targets the middle of the 1 A fast-recovery range for SMPS secondary rectification.
  • Match recovery time to switching frequency and check thermal derating in the actual layout — see ultra-fast recovery selection.
  • Compare 1F5G and 1F3G to match the recovery class to the topology.
  • The 1F4G balances recovery speed and forward drop for SMPS stages at 400 V, 1 A.
Good-Ark 1F4G fast recovery rectifier in R-1 axial package
The 1F4G is a 400 V, 1 A glass-passivated fast recovery rectifier in an R-1 axial package.

What Is a 1F4G Fast Recovery Rectifier Diode?

The 1F4G is a single fast recovery silicon rectifier designed to conduct current in one direction and block reverse voltage. It supports 1 A average forward current, 400 V repetitive peak reverse voltage, and a maximum reverse recovery time of 150 ns, using a glass-passivated junction inside an R-1 axial package. Unlike a bridge rectifier, which contains four interconnected diodes, the 1F4G is one discrete diode with two terminals — some product descriptions incorrectly call it a bridge rectifier, but circuit designers should treat it as a single fast recovery component.

In forward bias, the diode conducts current from the anode to the cathode; in reverse bias, it blocks current up to its rated reverse voltage apart from a small leakage current. The fast recovery construction helps the diode stop conducting shortly after the voltage reverses, reducing unwanted reverse current in switching circuits and making the 1F4G more suitable than a conventional slow rectifier for many medium-frequency power applications. Good-Ark Electronics manufactures the 1F4G as part of its 1F1G through 1F7G fast recovery rectifier family.

What Are the Main 1F4G Specifications?

The principal 1F4G ratings are 400 V repetitive peak reverse voltage, 1 A average forward current, 30 A non-repetitive surge current, 1.3 V maximum forward voltage, 5 µA maximum reverse leakage at 25 °C, and 150 ns maximum reverse recovery time, with an operating junction temperature range of −55 °C to +150 °C.

Parameter Symbol 1F4G rating
Repetitive peak reverse voltage VRRM 400 V
RMS reverse voltage VRMS 280 V
DC blocking voltage VDC 400 V
Average forward rectified current IF(AV) 1 A
Peak forward surge current IFSM 30 A
Maximum forward voltage VF 1.3 V at 1 A
Maximum reverse leakage IR 5 µA at 25 °C
Maximum reverse recovery time trr 150 ns
Typical junction capacitance CJ 12 pF
Junction temperature range TJ −55 °C to +150 °C
Package — R-1 axial

These values are maximum ratings or specified test-condition values rather than guaranteed performance under every operating condition. The 1 A average current rating depends on lead temperature, ambient conditions, PCB construction, airflow, conduction angle, and thermal management; the 30 A surge rating applies to a short 8.3 ms half-sine-wave event and does not mean the diode can continuously conduct 30 A. Repetitive inrush current, capacitive charging pulses, and poor cooling can raise the junction beyond its safe limit, so apply suitable voltage, current, and thermal margins instead of operating at absolute maximum ratings.

How Does the 1F4G Work in Switching Circuits?

The 1F4G conducts during forward bias and blocks during reverse bias, but stored charge prevents an ordinary silicon diode from turning off instantly; its fast recovery design removes that charge within a maximum of 150 ns under specified test conditions, limiting reverse current, switching loss, voltage stress, and electromagnetic noise. Immediately after polarity reverses, a diode can momentarily act like a conductor, creating recovery current through the diode and the associated switch — excessive recovery current may cause additional MOSFET switching loss, higher diode junction temperature, voltage overshoot from parasitic inductance, increased EMI, reduced efficiency, and greater stress on surrounding components.

A 150 ns recovery time makes the 1F4G significantly faster than many general-purpose rectifiers, but it is not automatically the best choice for every switching frequency: high-frequency converters may require an ultrafast diode, Schottky rectifier, silicon carbide diode, or synchronous rectification. Reverse recovery performance also depends on forward current, reverse current, junction temperature, current slew rate, and the manufacturer’s test method — compare datasheets under similar test conditions instead of judging components by the headline recovery-time number alone.

Which Applications Are Best Suited to the 1F4G?

The 1F4G is best suited to low-power circuits requiring 1 A conduction, up to 400 V reverse blocking, and faster switching than a general-purpose rectifier provides. Typical uses include small battery chargers, low-power switched-mode power supplies, auxiliary and standby power stages, DC-DC converter support circuits, freewheeling paths for relays and small inductive loads, reverse-polarity protection, clamp and snubber networks, general-purpose fast switching, industrial control power sections, and consumer and home-appliance electronics.

The device should not be selected solely because the normal load current is below 1 A: calculate peak current, repetitive surge current, reverse-voltage transients, switching frequency, duty cycle, and junction temperature. For transformerless or offline circuits, the 400 V rating may leave insufficient margin against rectified mains voltage and switching spikes — a higher-voltage member of the same family may be safer.

How Should Engineers Read the 1F4G Pinout and Package?

The 1F4G has two axial leads — an anode and a cathode — and the band printed around one end of the R-1 package identifies the cathode. Conventional current flows from the unbanded anode toward the banded cathode when the diode is forward-biased; reversing the device changes the circuit’s conduction direction. The R-1 through-hole package supports straightforward manual assembly and automated axial insertion, but its small body also restricts heat dissipation.

Installation considerations: confirm the cathode band before soldering; match the PCB footprint to the package drawing; avoid bending leads immediately next to the molded body; minimize mechanical stress during forming and insertion; keep sufficient lead length when thermal dissipation depends on the leads; follow the recommended soldering temperature and duration; and maintain clearance appropriate for the working voltage and environment. Good-Ark specifies high-temperature soldering capability of 260 °C for 10 seconds under defined conditions — not permission to expose the component body to unlimited heat.

How Does the 1F4G Compare with Other 1F-Series Diodes?

The 1F1G through 1F7G family shares a 1 A current rating and R-1 package, but reverse-voltage and recovery-time ratings vary. The 1F4G provides 400 V blocking and 150 ns recovery; higher-voltage versions offer more blocking margin, although maximum recovery time increases at 600 V and above.

Device VRRM IF(AV) IFSM Maximum trr Typical selection use
1F1G 50 V 1 A 30 A 150 ns Low-voltage switching
1F2G 100 V 1 A 30 A 150 ns 12 V and 24 V systems with margin
1F3G 200 V 1 A 30 A 150 ns Intermediate-voltage converters
1F4G 400 V 1 A 30 A 150 ns Medium-voltage fast rectification
1F5G 600 V 1 A 30 A 250 ns Higher-voltage power stages
1F6G 800 V 1 A 30 A 500 ns High blocking-voltage applications
1F7G 1,000 V 1 A 30 A 500 ns Maximum family voltage margin

A higher reverse-voltage rating is acceptable only when the replacement also meets the required current, recovery, forward-voltage, package, temperature, and surge specifications — for example, a 1F5G may provide more voltage margin than a 1F4G but has a slower specified recovery time, which can affect switching loss and EMI in a frequency-sensitive design.

Which Diodes Can Replace the 1F4G?

A valid 1F4G replacement must provide at least 400 V reverse blocking, 1 A average forward current, suitable surge capability, equal or faster recovery, compatible polarity and packaging, acceptable forward voltage, and sufficient temperature performance. Potential replacement selection should follow this order: confirm VRRM is 400 V or higher; confirm average and peak current ratings; compare reverse recovery time and test conditions; check forward voltage at the actual load current; review leakage at expected junction temperature; verify package dimensions, footprint, and lead spacing; evaluate thermal resistance and derating curves; confirm compliance and qualification requirements; and prototype the replacement in the real circuit.

A standard 1N4004 has similar headline voltage and current ratings but is a general-purpose rectifier and may recover too slowly for a switching application — it should not be treated as an automatic equivalent. An ultrafast 400 V diode may offer lower recovery loss, but its forward voltage, leakage, capacitance, or switching behavior may differ. A Schottky diode can be attractive at lower voltages, while 400 V Schottky availability and leakage characteristics require careful consideration. For automotive, aerospace, medical, or safety-critical designs, verify qualification status and change-control requirements rather than relying on a generic cross-reference list.

Why Do Thermal Design and Derating Matter?

Thermal design matters because forward loss, reverse leakage, and switching loss heat the diode junction; as temperature rises, leakage can increase and available current capability can decrease. A first estimate of conduction loss is P ≈ VF × IF: at 1 A and the maximum 1.3 V forward-drop value, instantaneous conduction loss could approach 1.3 W while conducting, though actual average loss depends on waveform, duty cycle, temperature, and dynamic resistance. Switching loss becomes more important as frequency rises and is influenced by reverse recovery charge, reverse voltage, switching frequency, and commutation speed.

Good design practice includes: avoiding continuous operation at the maximum current rating; providing extra reverse-voltage margin for overshoot; checking leakage at elevated temperature; evaluating repetitive rather than only single-event surge current; measuring case or lead temperature in the final enclosure; testing startup, overload, short-circuit, and abnormal conditions; and reviewing derating curves instead of relying only on the summary table.

Good-Ark Electronics Expert Views

“A fast recovery rectifier is only effective when its electrical and thermal characteristics match the real switching environment. For the 1F4G, the 150 ns recovery rating supports efficient medium-speed rectification, while the 400 V blocking capability and 30 A surge rating provide useful design flexibility. However, reliable selection still requires voltage derating, temperature evaluation, waveform measurement, and validation under startup and fault conditions. Good-Ark Electronics recommends comparing parts under equivalent test conditions and confirming performance in the finished power stage.”

Founded in 1990, Good-Ark Electronics supports rectifier development through an integrated supply chain covering wafer development, packaging, testing, manufacturing, and sales, with a broader portfolio that includes standard, fast recovery, Schottky, SiC, MOSFET, IGBT, and protection technologies.

Frequently Asked Questions

Is the 1F4G a bridge rectifier?

No. The 1F4G is a single two-terminal fast recovery rectifier diode. A bridge rectifier normally contains four diodes connected to provide full-wave rectification.

What does the band on a 1F4G indicate?

The band identifies the cathode. The opposite, unbanded terminal is the anode. In forward conduction, conventional current flows from the anode toward the cathode.

Can a 1N4004 replace a 1F4G?

Not automatically. Although both may be rated for 1 A and 400 V, the 1N4004 is generally a slower rectifier and may create excessive switching loss or reverse-recovery current in a fast-switching circuit.

Can the 1F4G continuously carry 30 A?

No. Its average forward-current rating is 1 A. The 30 A value is a short, non-repetitive surge rating under specified waveform conditions.

When should a faster diode be selected?

Choose an ultrafast, Schottky, SiC, or other suitable rectifier when the switching frequency, efficiency target, thermal limit, or EMI performance cannot be met with the 1F4G’s 150 ns recovery rating.

Official Resources

References


Copyright Suzhou Good-Ark Electronics Co., Ltd. All Rights Reserved