SMD code 40-
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.
74 parts are printed 40-
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.
BAS40TSSOD-523Schottky diode, 2 pins, PanjitSchottky diodeSOD-5232 pinsPanjit
- What it is
- Schottky diode
- Maker
- Panjit
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BZX584C5V6SOD-523Zener diode, 2 pins, Formosa MicrosemiZener diodeSOD-5232 pinsFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C16SOD-523Zener diode, 2 pins, Formosa MicrosemiZener diodeSOD-5232 pinsFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
DTC014EEBSOT-416Digital transistor (NPN, resistors built in), 3 pins, ROHMDigital transistor (NPN, resistors built in)SOT-4163 pinsROHM
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- ROHM
- Package
- SOT-416
- Pins
- 3
- Details
- NPN 100mA 50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTC014EMSOT-723Digital transistor (NPN, resistors built in), 3 pins, ROHMDigital transistor (NPN, resistors built in)SOT-7233 pinsROHM
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- ROHM
- Package
- SOT-723
- Pins
- 3
- Details
- NPN 100mA 50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTC014EUBSOT-323Digital transistor (NPN, resistors built in), 3 pins, ROHMDigital transistor (NPN, resistors built in)SOT-3233 pinsROHM
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- ROHM
- Package
- SOT-323
- Pins
- 3
- Details
- NPN 100mA 50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
ET5H540SOT-23-5LDO regulator, 5 pins, ETEKLDO regulatorSOT-23-55 pinsETEK
- What it is
- LDO regulator
- Maker
- ETEK
- Package
- SOT-23-5
- Pins
- 5
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
hFE(2)SOT-23-6Transistor, 6 pins, YFWTransistorSOT-23-66 pinsYFW
- What it is
- Transistor
- Maker
- YFW
- Package
- SOT-23-6
- Pins
- 6
- Details
- Bipolar transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor.
LD39020DTPU40RDFNLDO regulator, STMicroelectronicsLDO regulatorDFNNot recordedSTMicroelectronics
- What it is
- LDO regulator
- Maker
- STMicroelectronics
- Package
- DFN
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
P4SOD40ASOD-123TVS diode, 2 pins, WeEn SemiconductorsTVS diodeSOD-1232 pinsWeEn Semiconductors
- What it is
- TVS diode
- Maker
- WeEn Semiconductors
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
PMBFJ110SOT-23JFET, 3 pins, NXPJFETSOT-233 pinsNXP
- What it is
- JFET
- Maker
- NXP
- Package
- SOT-23
- Pins
- 3
- Details
- N-channel junction FETs
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: JFET.
4 more parts have no package on record
BAS40M5Schottky diode, Taiwan SemiconductorSchottky diodeNot recordedNot recordedTaiwan Semiconductor
- What it is
- Schottky diode
- Maker
- Taiwan Semiconductor
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BZX584B5V6Zener diode, Formosa MicrosemiZener diodeNot recordedNot recordedFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584B16Zener diode, Formosa MicrosemiZener diodeNot recordedNot recordedFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
NUF4000MUESD protection diode, onsemiESD protection diodeNot recordedNot recordedonsemi
- What it is
- ESD protection diode
- Maker
- onsemi
- Package
- Not recorded
- Pins
- Not recorded
- Details
- 4-Channel EMI Filter with Integrated ESD Protection
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection 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.
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.
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.
Digital transistor
Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.
Working, it reads
Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.
Dead, it reads
- Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
- From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
- Base to emitter near 0 Ω: failed short.
- 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:
- The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
- Watch for:
- On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Voltage regulator
Voltage, board powered, black probe on ground. Then ohms with the power off.
Working, it reads
Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.
Dead, it reads
- Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
- Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
- Power off, input to output near 0 Ω: shorted.
- On the board:
- An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
- Compare:
- The same regulator on another rail or another board shows the right voltages and the right resistances.
- Watch for:
- Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.
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.
TVS or ESD protection diode
Diode range, from the protected line to ground, part lifted if you can.
Working, it reads
A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.
Dead, it reads
- From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
- A reading both ways on a one-way part: leaky.
- A one-way part open both ways: failed open.
- On the board
- , a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
- Compare:
- The same part on the next line or connector pin is the healthy reading to compare with.
- Watch for:
- A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
JFET
Ohms range for drain to source, diode range for the gate, part lifted.
Working, it reads
Drain to source conducts both ways at a few hundred ohms, depending on the part, and some meters beep on it. The gate reads one junction to drain and to source, about 0.6 to 0.7 V, and open the other way.
Dead, it reads
- The gate the same both ways to drain or source, near 0 V with a continuous beep: gate shorted.
- Drain to source open: the channel has 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:
- Drain to source resistance varies from part to part. An identical part elsewhere on the board shows what is normal.
- Watch for:
- A good channel can beep like a short between drain and source. That is normal; the gate junction says whether it has failed.
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 40-
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 2 more parts.
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