SMD code A4- 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.
36 parts in SOT-23 are printed A4-
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:
MMBD5148N3SOT-23Switching diode, CYStekSwitching diodeCYStek
- What it is
- Switching diode
- Maker
- CYStek
- Package
- SOT-23
- Pins
- 3
- Details
- 100 V switching diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-LBAV70LT1GSOT-23Switching diode, LRCSwitching diodeLRC
- What it is
- Switching diode
- Maker
- LRC
- Package
- SOT-23
- Pins
- 3
- Details
- Switching diode, VR 100 V, IF 200 mA, VF Max 1.25 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-LBAV70LT1G-SSOT-23Switching diode, LRCSwitching diodeLRC
- What it is
- Switching diode
- Maker
- LRC
- Package
- SOT-23
- Pins
- 3
- Details
- Switching diode, VR 100 V, IF 200 mA, VF Max 1.25 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
SBAV70LSOT-23Switching diode, onsemiSwitching diodeonsemi
- What it is
- Switching diode
- Maker
- onsemi
- Package
- SOT-23
- Pins
- 3
- Details
- Dual Switching Diode Common Cathode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
SCS202NKSOT-23Switching diode, SeCoSSwitching diodeSeCoS
- What it is
- Switching diode
- Maker
- SeCoS
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
TBAV70SOT-23Switching diode, Galaxy MicroelectronicsSwitching diodeGalaxy Microelectronics
- What it is
- Switching diode
- Maker
- Galaxy Microelectronics
- Package
- SOT-23
- Pins
- 3
- Details
- 0.2A, 100V, Surface Mount Small Signal Switching Diodes
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BAV70N3SOT-23Switching diode, CYStekSwitching diodeCYStek
- What it is
- Switching diode
- Maker
- CYStek
- Package
- SOT-23
- Pins
- 3
- Details
- 110 V switching diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BTA1037N3SOT-23PNP transistor, CYStekPNP transistorCYStek
- What it is
- PNP transistor
- Maker
- CYStek
- Package
- SOT-23
- Pins
- 3
- Details
- -65 V, -0.15 A PNP transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: PNP transistor.
1S2836SOT-23NEC ElectronicsNot recordedNEC Electronics
- What it is
- Not recorded
- Maker
- NEC Electronics
- Package
- SOT-23
- Pins
- 3
- Details
- Si-diode: Dual, Sw, Fast, 75V, 150mA, <4ms
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
AO3404SOT-23N-channel MOSFET, AlphaN-channel MOSFETAlpha
- What it is
- N-channel MOSFET
- Maker
- Alpha
- Package
- SOT-23
- Pins
- 3
- Details
- N-channel MOSFET, 30 V
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
BAV70LT1SOT-23onsemiNot recordedonsemi
- What it is
- Not recorded
- Maker
- onsemi
- Package
- SOT-23
- Pins
- 3
- Details
- Monolithic Dual Switching Diode
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
BAV70PTSOT-23Chenmko EnterpriseNot recordedChenmko Enterprise
- What it is
- Not recorded
- Maker
- Chenmko Enterprise
- Package
- SOT-23
- Pins
- 3
- Details
- Diode: Dual, Sw, 75V, 250mA, Vf<1.25V(150mA), 4ns
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
BB404ASOT-23ITT IntermetallNot recordedITT Intermetall
- What it is
- Not recorded
- Maker
- ITT Intermetall
- Package
- SOT-23
- Pins
- 3
- Details
- Capacitance diode: Dual, 10V, 43.5..27.5pF(2..8V), 100MHz
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
CHN202KPTSOT-23Chenmko EnterpriseNot recordedChenmko Enterprise
- What it is
- Not recorded
- Maker
- Chenmko Enterprise
- Package
- SOT-23
- Pins
- 3
- Details
- Diode: Dual, Sw, 80V, 100mA, Vf<1.2V(100mA), 4ns
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
HSMS-2804SOT-23Avago / BroadcomNot recordedAvago / Broadcom
- What it is
- Not recorded
- Maker
- Avago / Broadcom
- Package
- SOT-23
- Pins
- 3
- Details
- dual cc HP2800 schottky
- Source
- Published code list
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.
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.
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.
N-channel MOSFET
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.
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. Often all three pins end up shorted together.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. 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.
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