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SMD code AJ in SOT-223

Marking codes are not standardised, and the same code is reused by unrelated makers for unrelated parts. Below is every part in our tables printed with it, and any printed with a code that is easy to misread as it, from the manufacturers' own marking tables and published code lists.

Not sure which one you have?

Answer up to 4 quick questions and these 47 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BCP56L3SOT-223NPN transistor, 4 pins, CYStekNPN transistor4 pinsCYStek
    What it is
    NPN transistor
    Maker
    CYStek
    Package
    SOT-223
    Pins
    4
    Details
    80 V, 1 A NPN transistor
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: NPN transistor.

  • BTA1727L3SOT-223PNP transistor, 4 pins, CYStekPNP transistor4 pinsCYStek
    What it is
    PNP transistor
    Maker
    CYStek
    Package
    SOT-223
    Pins
    4
    Details
    -400 V, -0.3 A PNP transistor
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: PNP transistor.

  • BTD5213L3SOT-223NPN transistor, 4 pins, CYStekNPN transistor4 pinsCYStek
    What it is
    NPN transistor
    Maker
    CYStek
    Package
    SOT-223
    Pins
    4
    Details
    100 V, 1 A NPN transistor
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: NPN transistor.

  • TFL56SOT-223NPN transistor, Tin Far ElectronicNPN transistorNot recordedTin Far Electronic
    What it is
    NPN transistor
    Maker
    Tin Far Electronic
    Package
    SOT-223
    Pins
    Not recorded
    Details
    NPN transistor: AF, GP, 80V, 1A, 2W, B=100..400, 125MHz
    Source
    Published code list

    Is it dead? The meter test is below: NPN transistor.

  • 11 more parts have no package on record. Nothing rules them out, so they stay.
    • BZX884B4V3LZener diode, VishayZener diodeNot recordedVishay
      What it is
      Zener diode
      Maker
      Vishay
      Package
      Not recorded
      Pins
      Not recorded
      Details
      4.3 V Zener diode
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Zener diode.

    • BZX884B12Zener diode, Good-ArkZener diodeNot recordedGood-Ark
      What it is
      Zener diode
      Maker
      Good-Ark
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode, VZ 12 V, 0.25 W
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Zener diode.

    • BZX884B12VZener diode, RectronZener diodeNot recordedRectron
      What it is
      Zener diode
      Maker
      Rectron
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Zener diode.

    • J111N-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J111-D26ZN-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J111-D74ZN-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J112N-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J112-D26ZN-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J112-D27ZN-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J112-D74ZN-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

    • J113N-channel MOSFET, onsemiN-channel MOSFETNot recordedonsemi
      What it is
      N-channel MOSFET
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel Switch J111, J112, J113
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

Is it dead? One meter test per kind

Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.

NPN transistor

Diode range, part lifted or its base leg off the pad.

Working, it reads

Red probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

Dead, it reads

  • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
  • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
  • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
  • A reading the wrong way round, where it should be open: leaky.
On the board
this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

PNP transistor

Diode range, part lifted or its base leg off the pad.

Working, it reads

Black probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

Dead, it reads

  • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
  • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
  • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
  • A reading the wrong way round, where it should be open: leaky.
On the board
this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Zener diode

Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.

Working, it reads

About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.

Dead, it reads

  • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
  • Open both ways, forward too: failed open.
  • Holds well off its rated voltage on the supply test: drifted.
  • A soft knee, or a voltage that creeps on the supply test: leaky.
On the board
this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

N-channel MOSFET

Diode range, part lifted. Test drain to source first, then short gate to source and test again.

Working, it reads

Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

Dead, it reads

  • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
  • The gate reads low to source or drain: gate shorted. Often all three pins end up shorted together.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. Lift a leg to be sure.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
The diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Codes that begin with AJ

For a marking with its end worn or burnt off. Each code has a page of its own.

Codes not listed here are printed on 22 more parts.

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