SMD code E1x in SOT-23
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.
The last letter, x, is lower case, which on NXP and Philips parts is a date or factory code, so it was set aside and E1 was searched.
25 parts in SOT-23 are printed E1x
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.
all SOT-23, 3 pins. What differs:
LDTD123TLT1GSOT-23Digital transistor (NPN, resistors built in), LRCDigital transistor (NPN, resistors built in)LRC
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- LRC
- Package
- SOT-23
- Pins
- 3
- Details
- Digital transistor (bias resistors built in), NPN, IC 500 mA, VCEO 40 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
MMBZ5231ASOT-23Zener diode, PanjitZener diodePanjit
- What it is
- Zener diode
- Maker
- Panjit
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
MMBZ5231A-HFSOT-23Zener diode, ComchipZener diodeComchip
- What it is
- Zener diode
- Maker
- Comchip
- Package
- SOT-23
- Pins
- 3
- Details
- 5.1 V 0.35 mW zener diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
MMBZ5231BSOT-23Zener diode, DC ComponentsZener diodeDC Components
- What it is
- Zener diode
- Maker
- DC Components
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
MMBZ5231B-AUSOT-23Zener diode, PanjitZener diodePanjit
- What it is
- Zener diode
- Maker
- Panjit
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
S-LDTD123TLT1GSOT-23Digital transistor (NPN, resistors built in), LRCDigital transistor (NPN, resistors built in)LRC
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- LRC
- Package
- SOT-23
- Pins
- 3
- Details
- Digital transistor (bias resistors built in), NPN, IC 500 mA, VCEO 40 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
AP8821C-41GCSOT-23Voltage supervisor, Anwell SemiconductorVoltage supervisorAnwell Semiconductor
- What it is
- Voltage supervisor
- Maker
- Anwell Semiconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.1V±2%, -Reset PPO, H-free
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
AP8821C-41PCSOT-23Voltage supervisor, Anwell SemiconductorVoltage supervisorAnwell Semiconductor
- What it is
- Voltage supervisor
- Maker
- Anwell Semiconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.1V±2%, -Reset PPO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
BFS17SOT-23TELEFUNKEN Aktiengesellschaft / Thomson-CSF / Zetex plcNot recordedTELEFUNKEN Aktiengesellschaft / Thomson-CSF / Zetex plc
- What it is
- Not recorded
- Maker
- TELEFUNKEN Aktiengesellschaft / Thomson-CSF / Zetex plc
- Package
- SOT-23
- Pins
- 3
- Details
- equivalent BFW92
- Source
- Published code list
Is it dead? The meter test is below: This part.
BFS17LSOT-23onsemiNot recordedonsemi
- What it is
- Not recorded
- Maker
- onsemi
- Package
- SOT-23
- Pins
- 3
- Details
- Si-npn: VHF.UHF, 25V, 25mA, 330mW, B=25..100, >1GHz
- Source
- Published code list
Is it dead? The meter test is below: This part.
BL8552CB3TR21SOT-23LDO regulator, Shanghai BellingLDO regulatorShanghai Belling
- What it is
- LDO regulator
- Maker
- Shanghai Belling
- Package
- SOT-23
- Pins
- 3
- Details
- Linear voltage regulator IC: LDO, 2.1V±2%, 300mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
BL8552CB3TR31SOT-23LDO regulator, Shanghai BellingLDO regulatorShanghai Belling
- What it is
- LDO regulator
- Maker
- Shanghai Belling
- Package
- SOT-23
- Pins
- 3
- Details
- Linear voltage regulator IC: LDO, 3.1V±2%, 300mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
CDSOT23-T03SOT-23BournsNot recordedBourns
- What it is
- Not recorded
- Maker
- Bourns
- Package
- SOT-23
- Pins
- 3
- Details
- TVS Diode (3.3V unidirectional)
- Source
- Published code list
Is it dead? The meter test is below: TVS or ESD protection diode.
EC95808C41B1NSOT-23Voltage supervisor, E-CMOSVoltage supervisorE-CMOS
- What it is
- Voltage supervisor
- Maker
- E-CMOS
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.1V±2%, -Reset PPO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
ELM9741NBBSOT-23Voltage supervisor, ELM TechnologyVoltage supervisorELM Technology
- What it is
- Voltage supervisor
- Maker
- ELM Technology
- Package
- SOT-23
- Pins
- 3
- Details
- Voltage detector IC: 4.1V±2.5%, +Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
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.
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.
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.
Integrated circuit
Voltage with the board powered; ohms from each pin to ground with it off.
Working, it reads
Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.
Dead, it reads
- A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
- Supply present, output stuck: failed, or its load has.
- On the board:
- A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
- Compare:
- The surest reference is the same IC on a working board, measured pin by pin.
- Watch for:
- Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
This part
Diode range and ohms range, part lifted.
Working, it reads
Depends on what it is. The datasheet, or an identical part, says.
Dead, it reads
- Between two pins, the same reading both ways, near 0 V with a continuous beep: shorted.
- Open between every pair of pins: failed open, or a part that reads open when working.
- 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.
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.
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.
Printed with a code easy to misread as E1x
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes that begin with E1x
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 376 more parts.
Did you find your part?
Open this in the search to correct a character or try another package.