SMD marking

48in SOT-323

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.

The only part printed 48 in this package in our tables

PDTC123EU

What it is: Digital transistor (NPN, resistors built in)
Maker: Nexperia
Package: SOT-323
Pins: 3
Details: 50 V, 100 mA NPN resistor-equipped transistor; R1 = 2.2 kΩ, R2 = 2.2 kΩ
Source: From the manufacturer's datasheet

Is it dead?

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:: 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.

Datasheet

12 more parts have codes that begin with 48

Codes that begin with 48

For a marking with its end worn or burnt off. Each one shows its full printed code.

BC848AWprinted 48ASOT-323Transistor, 3 pins, PanjitTransistor3 pinsPanjit
Printed 48A. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-323
Pins
3
Details
Bipolar transistor
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BC848AW, opens in a new tab
BC848AW-AUprinted 48ASOT-323Transistor, 3 pins, PanjitTransistor3 pinsPanjit
Printed 48A. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-323
Pins
3
Details
Bipolar transistor
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BC848AW-AU, opens in a new tab
BC848BWprinted 48BSOT-323Transistor, 3 pins, PanjitTransistor3 pinsPanjit
Printed 48B. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-323
Pins
3
Details
SMD General Purpose NPN Transistors
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BC848BW, opens in a new tab
BC848CWprinted 48CSOT-323Transistor, 3 pins, PanjitTransistor3 pinsPanjit
Printed 48C. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-323
Pins
3
Details
SMD General Purpose NPN Transistors
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BC848CW, opens in a new tab
BC848CW-AUprinted 48CSOT-323Transistor, 3 pins, PanjitTransistor3 pinsPanjit
Printed 48C. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-323
Pins
3
Details
Bipolar transistor
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BC848CW-AU, opens in a new tab
7 more parts have no package on record. Nothing rules them out, so they stay.
- PJQ4848P-AUprinted 4848MOSFET, PanjitMOSFETNot recordedPanjit
  Printed 4848. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  MOSFET
  Maker
  Panjit
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PJQ4848P-AU, opens in a new tab
- LMR51430XDDCprinted 4BXPDC-DC converter, 6 pins, Texas InstrumentsDC-DC converter6 pinsTexas Instruments
  Printed 4BXP. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  DC-DC converter
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  6
  Details
  SIMPLE SWITCHER® Power Converter 4.5-V to 36-V, 3-A, Synchronous Buck Converter in a SOT-23 Package
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor LMR51430XDDC, opens in a new tab
- LMR51430XFDDCprinted 4BXFDC-DC converter, 6 pins, Texas InstrumentsDC-DC converter6 pinsTexas Instruments
  Printed 4BXF. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  DC-DC converter
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  6
  Details
  SIMPLE SWITCHER® Power Converter 4.5-V to 36-V, 3-A, Synchronous Buck Converter in a SOT-23 Package
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor LMR51430XFDDC, opens in a new tab
- LMR51430YDDCprinted 4BYPDC-DC converter, 6 pins, Texas InstrumentsDC-DC converter6 pinsTexas Instruments
  Printed 4BYP. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  DC-DC converter
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  6
  Details
  SIMPLE SWITCHER® Power Converter 4.5-V to 36-V, 3-A, Synchronous Buck Converter in a SOT-23 Package
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor LMR51430YDDC, opens in a new tab
- LMR51430YFDDCprinted 4BYFDC-DC converter, 6 pins, Texas InstrumentsDC-DC converter6 pinsTexas Instruments
  Printed 4BYF. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  DC-DC converter
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  6
  Details
  SIMPLE SWITCHER® Power Converter 4.5-V to 36-V, 3-A, Synchronous Buck Converter in a SOT-23 Package
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor LMR51430YFDDC, opens in a new tab
- PLZ4V3Bprinted 4B3Zener diode, VishayZener diodeNot recordedVishay
  Printed 4B3. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  Zener diode
  Maker
  Vishay
  Package
  Not recorded
  Pins
  Not recorded
  Details
  4.3 V Zener diode
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PLZ4V3B, opens in a new tab
- PLZ4V7Bprinted 4B7Zener diode, VishayZener diodeNot recordedVishay
  Printed 4B7. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  What it is
  Zener diode
  Maker
  Vishay
  Package
  Not recorded
  Pins
  Not recorded
  Details
  4.7 V Zener diode
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PLZ4V7B, opens in a new tab

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