Fast recovery diodes (FRD)

A fast recovery diode is a rectifier designed to stop conducting quickly when it is reverse-biased. In hard-switched power converters that speed is not a luxury: slow turn-off means large reverse currents, switching losses and noise. Haiben stocks a dedicated Fast Recovery Diodes (FRD) category within its discrete semiconductor range, alongside switching diodes, Schottky diodes and rectifier diodes. This page explains the device class, how it compares with neighbouring families, where it is specified, and how stocked models are confirmed at quotation.

Reverse recovery: the problem fast recovery diodes solve

Every PN junction stores charge while it conducts in forward direction. When the voltage across it reverses, that stored charge must be removed before the device blocks. The result is a brief but real reverse current that flows in the wrong direction, followed by a snap or soft transition as the junction recovers.

This reverse recovery time, trr, has consequences in the circuit. The reverse current adds to the turn-on current of the opposing switch, so the switch dissipates more energy per transition. The recovery event also produces a current step (di/dt) that excites parasitic inductance in the layout, generating voltage spikes and electromagnetic interference. In a hard-switched converter running at tens of kilohertz or more, these effects repeat on every cycle.

A fast recovery diode is engineered to shorten trr and reduce stored charge. Faster recovery narrows the window in which reverse current flows, reducing switching loss in the diode itself and in the transistor that pairs with it. A well-behaved recovery also eases the job of snubbers and EMI filtering. In some circuits a snubber can be reduced or removed once recovery is faster and softer.

Fast recovery vs standard rectifier vs Schottky

The three families trade off differently, and selection starts with frequency, voltage and current.

• Standard rectifier diodes are optimised for forward conduction and surge handling at mains frequencies. Their recovery time is comparatively long, so at high switching frequency they cause large reverse currents and losses. They remain a good fit for 50/60 Hz rectification and low-frequency paths.
• Fast recovery diodes reduce trr and stored charge while retaining a PN junction, so they handle higher reverse voltages than Schottky parts typically can. They are the usual choice in hard-switched converters where the diode must block appreciable voltage and recover quickly each cycle.
• Schottky diodes are majority-carrier devices with effectively no stored minority charge, so they switch very fast and have a low forward drop. The trade-offs are higher reverse leakage, temperature sensitivity and a lower practical voltage ceiling. They suit low-voltage, high-frequency work.

For fast signal-level work rather than power conversion, small switching diodes such as the VC1N4148WB cover logic-level and signal-routing roles. Choosing between families comes down to the datasheet: trr and recovery charge for the diode, peak reverse voltage, forward current and thermal behaviour for the application.

Where FRDs are specified

Fast recovery diodes appear wherever a PN diode must block significant reverse voltage and turn off quickly:

• Freewheel and clamp positions in switch-mode power supplies and DC-DC converters.
• Snubber and clamp networks around switching transistors, where fast, controlled recovery limits spike energy.
• Output rectification in converters where Schottky voltage ratings are insufficient.
• Inverter and motor-drive circuits that need rugged reverse blocking with manageable recovery loss.
• Pulse and blocking circuits where recovery time shapes waveform integrity.

When comparing candidates, check trr and recovery charge at the actual forward current and di/dt, not only at the datasheet's headline test condition. Confirm peak reverse voltage with margin for switching spikes, and verify thermal resistance against the real duty cycle. Layout matters too: short loops reduce the parasitic inductance that turns fast recovery into ringing.

The catalogue range and datasheet confirmation

Haiben's official company catalogue carries a dedicated Fast Recovery Diodes (FRD) category within its discrete semiconductor range, alongside switching diodes like the VC1N4148WB, Schottky diodes and rectifier diodes. Because the FRD range is defined by its catalogue category, this page makes no claims about specific part numbers, package options or recovery-time figures. Stocked models and their datasheets are confirmed at quotation, so the purchasing team can match a part to the engineer's requirements before ordering.

For samples, cross-reference support or volume pricing, send the target specification to our sales team and we will confirm which Weforsemi line or stocked models apply.

Frequently asked questions

What is the difference between a fast recovery diode and a standard rectifier?

A fast recovery diode is designed to reduce reverse recovery time and stored charge, so it turns off faster when reverse-biased. A standard rectifier is optimised for forward conduction and surge handling at low frequency and typically recovers more slowly. At high switching frequencies that slower recovery increases losses and EMI.

When should I choose a Schottky diode instead of a fast recovery diode?

Schottky diodes have effectively no minority-carrier recovery and a low forward drop, which suits low-voltage, high-frequency circuits. Fast recovery diodes are generally preferred where higher reverse voltage blocking is required. The decision depends on voltage, current, frequency and thermal conditions in your design.

How do I confirm which FRD part numbers and specifications are stocked?

Stocked models and their datasheets are confirmed at quotation. Send your required voltage, current, recovery time and package preferences to our sales team, and we will confirm which models, including any Weforsemi line options, are available.