Overview

The 1N4148 is the classic fast small-signal silicon switching diode. It lives in nearly every hobbyist parts bin next to the 1N400x family: where the 1N4007 is a slow 1 A power rectifier, the 1N4148 is a high-speed, low-current diode for logic clamping, steering, freewheeling on small inductors, and RF/signal work.

Rated for 100 V peak reverse voltage and roughly 200 mA continuous forward current, its defining number is the ~4 ns reverse recovery time — fast enough that it stays useful well into MHz switching, unlike power rectifiers.

Quick reference

TypeSilicon small-signal switching diode
PackageDO-35 (DO-204AH) axial glass
Cathode markingBlack / painted band = cathode (−)
Peak reverse voltage VR100 V
Average forward current IF200 mA
Forward voltage Vf≤ 1.0 V at 10 mA
Reverse recovery trr4 ns max
Junction capacitance4 pF typ at 0 V, 1 MHz

Polarity

Info

The band on the glass body marks the cathode (−). Forward current flows anode → cathode when the anode is ~0.6–0.7 V above the cathode.

text
   Anode (+)              Cathode (−)
                     (band)
      ────────┤├────────

Key parameters

ParameterSymbolMinTypMaxUnitConditions
Breakdown / reverse voltageVR100——VIR = 100 µA
Forward voltageVf——1.0VIF = 10 mA
Forward voltageVf——1.0VIF = 100 mA (1N4448 class)
Reverse leakageIR——5.0µAVR = 75 V, TA = 25 °C
Reverse recovery timetrr——4nsIF = 10 mA, VR = 6 V, Irr = 1 mA
CapacitanceCT——4pFVR = 0 V, f = 1 MHz
Average rectified currentIF(AV)——200mA
Peak surge currentIFSM——1.0Apulse

Forward & reverse characteristics

  • Forward: Conducts when Vanode − Vcathode exceeds ~0.6–0.7 V; voltage rise is steeper than a Schottky but recovery is much faster than a 1N400x.
  • Reverse: Blocks up to 100 V with microamp-level leakage at room temperature; leakage rises strongly with junction temperature.

Variants

PartNotes
1N4148Default DO-35 hobbyist stock part
1N914Closely related / often co-documented with 1N4148
1N4448Same family; slightly different Vf / current binning
SOD-323 / SOD-523 SMTSurface-mount “WS” style equivalents (e.g. 1N4148WS)

Typical circuits

text
Logic clamp / input protection:

  MCU GPIO ──┬──>|-- 1N4148 ── +3.3 V / +5 V
             │     (cathode toward rail)
             └──>|-- 1N4148 ── GND
                   (anode toward GND)

Steering / OR-ing two open-collector signals:

  SIG_A ──>|--┐
              ├── OUT
  SIG_B ──>|--┘

Common mistakes

  • Using a 1N4007 where speed matters: A 1N400x has microsecond-class recovery and large capacitance — wrong for fast logic edges or RF. Use the 1N4148 (or a Schottky) instead.
  • Expecting 1 A capability: Continuous rating is ~200 mA. For motor/relay flyback at higher currents, use a 1N400x or a proper catch diode sized for the load.
  • Reversed band in a clamp: Band (cathode) must face the positive rail in a high-side clamp; reverse it and you short the supply through the diode.

Notes

  • Electrically interchangeable with most “1N914-class” glass signal diodes in hobby circuits; check Vf / trr only when matching a precision timing or RF design.
  • Datasheet cited is onsemi’s combined 1N914 / 1N4148 / 1N4448 family PDF.

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