SMD code L4-
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.
154 parts are printed L4-
Not sure which one you have?
Answer up to 4 quick questions and these 50 parts are ranked, with a meter test that settles it. It works on a dead part too.
2SC1623 L4SOT-23NPN transistor, 3 pins, HottechNPN transistorSOT-233 pinsHottech
- What it is
- NPN transistor
- Maker
- Hottech
- Package
- SOT-23
- Pins
- 3
- Details
- NPN transistor, 50 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: NPN transistor.
2SC1623-L4SOT-23Transistor, 3 pins, YFWTransistorSOT-233 pinsYFW
- What it is
- Transistor
- Maker
- YFW
- Package
- SOT-23
- Pins
- 3
- Details
- Bipolar transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor.
2SC4177-L4SOT-323Transistor, 3 pins, YFWTransistorSOT-3233 pinsYFW
- What it is
- Transistor
- Maker
- YFW
- Package
- SOT-323
- Pins
- 3
- Details
- Bipolar transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor.
ABAS521-HFSOD-523Switching diode, 2 pins, ComchipSwitching diodeSOD-5232 pinsComchip
- What it is
- Switching diode
- Maker
- Comchip
- Package
- SOD-523
- Pins
- 2
- Details
- 300 V, 250 mA switching diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
AO3494SOT-23MOSFET, 3 pins, Alpha & Omega SemiconductorMOSFETSOT-233 pinsAlpha & Omega Semiconductor
- What it is
- MOSFET
- Maker
- Alpha & Omega Semiconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Low-voltage (12-30 V) MOSFET
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: MOSFET.
BAL99SOT-23Switching diode, 3 pins, Formosa MicrosemiSwitching diodeSOT-233 pinsFormosa Microsemi
- What it is
- Switching diode
- Maker
- Formosa Microsemi
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BAS521SOD-523Switching diode, 2 pins, Galaxy MicroelectronicsSwitching diodeSOD-5232 pinsGalaxy Microelectronics
- What it is
- Switching diode
- Maker
- Galaxy Microelectronics
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BAS521-CSOD-523Switching diode, 2 pins, SeCoSSwitching diodeSOD-5232 pinsSeCoS
- What it is
- Switching diode
- Maker
- SeCoS
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BAT54SOT-23Schottky diode, 3 pins, Taitron ComponentsSchottky diodeSOT-233 pinsTaitron Components
- What it is
- Schottky diode
- Maker
- Taitron Components
- Package
- SOT-23
- Pins
- 3
- Pinout
- 1 anode
- 2 not connected
- 3 cathode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54-AUSOT-23Schottky diode, 3 pins, PanjitSchottky diodeSOT-233 pinsPanjit
- What it is
- Schottky diode
- Maker
- Panjit
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54-CSOT-23Schottky diode, 3 pins, SeCoSSchottky diodeSOT-233 pinsSeCoS
- What it is
- Schottky diode
- Maker
- SeCoS
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54-P2-HFSOT-23Schottky diode, 3 pins, ComchipSchottky diodeSOT-233 pinsComchip
- What it is
- Schottky diode
- Maker
- Comchip
- Package
- SOT-23
- Pins
- 3
- Details
- 30 V, 0.2 A Schottky barrier diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54H-CSOD-323Schottky diode, 2 pins, SeCoSSchottky diodeSOD-3232 pinsSeCoS
- What it is
- Schottky diode
- Maker
- SeCoS
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54STSOT-523Schottky diode, 3 pins, onsemiSchottky diodeSOT-5233 pinsonsemi
- What it is
- Schottky diode
- Maker
- onsemi
- Package
- SOT-523
- Pins
- 3
- Details
- 0.2A, 30V, Surface Mount Small Signal Schottky Diodes
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BAT54ST-CSOT-523Schottky diode, 3 pins, SeCoSSchottky diodeSOT-5233 pinsSeCoS
- What it is
- Schottky diode
- Maker
- SeCoS
- Package
- SOT-523
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
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.
Bipolar transistor
Diode range, part lifted or its base leg off the pad.
Working, it reads
From the base, one probe colour 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.
Silicon diode
Diode range, part lifted or one leg off the pad. Red probe on the anode.
Working, it reads
About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.
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: failed open.
- A reading the wrong way round as well: 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 three-pin body can hold two diodes. With a common pin they read two junctions from that pin, just like a transistor; in series they read two drops end to end. Test each pair the datasheet names.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
MOSFET
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.
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.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, which reads as that resistor and is not a fault. 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.
Schottky diode
Diode range, part lifted or one leg off the pad. Red probe on the anode.
Working, it reads
About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.
Dead, it reads
- The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
- A reading the wrong way round as well: leaky.
- Open both ways: failed open.
- 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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Printed with a code easy to misread as L4-
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes not listed here are printed on 4 more parts.
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