SMD code AO in SOT-89
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.
3 parts in SOT-89 are printed AO
Not sure which one you have?
Answer up to 4 quick questions and these 7 parts are ranked, with a meter test that settles it. It works on a dead part too.
2SC2880-OSOT-89NPN transistor, 3 pins, ToshibaNPN transistor3 pinsToshiba
- What it is
- NPN transistor
- Maker
- Toshiba
- Package
- SOT-89
- Pins
- 3
- Details
- Si-npn: HV, 150V, 50mA, 500mW, B=70..140, 120MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
2SC2880OSOT-893 pins, ToshibaNot recorded3 pinsToshiba
- What it is
- Not recorded
- Maker
- Toshiba
- Package
- SOT-89
- Pins
- 3
- Source
- Published code list
Is it dead? The meter test is below: This part.
KTC4372-OSOT-89NPN transistor, 3 pins, KECNPN transistor3 pinsKEC
- What it is
- NPN transistor
- Maker
- KEC
- Package
- SOT-89
- Pins
- 3
- Details
- Si-npn: HV, Sw, 150V, 50mA, 500mW, B=70..140, 120MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
4 more parts have no package on record. Nothing rules them out, so they stay.
BZX884B6V2LZener diode, VishayZener diodeNot recordedVishay
- What it is
- Zener diode
- Maker
- Vishay
- Package
- Not recorded
- Pins
- Not recorded
- Details
- 6.2 V Zener diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
2SA1980EF-OPNP transistor, AUK SemiconductorPNP transistorNot recordedAUK Semiconductor
- What it is
- PNP transistor
- Maker
- AUK Semiconductor
- Package
- Not recorded
- Pins
- Not recorded
- Details
- PNP transistor: GP, 50V, 150mA, 150mW, B=70..140, 80MHz
- Source
- Published code list
Is it dead? The meter test is below: PNP transistor.
BFP4905 pins, InfineonNot recorded5 pinsInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- Not recorded
- Pins
- 5
- Source
- Published code list
Is it dead? The meter test is below: This part.
MA5Z300-HZener diode, PanasonicZener diodeNot recordedPanasonic
- What it is
- Zener diode
- Maker
- Panasonic
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Zener diode: 300V, Iz=0.1mA, 150mW
- Source
- Published code list
Is it dead? The meter test is below: Zener 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.
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.
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.
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.
Printed with a code easy to misread as AO
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 1 more part.
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