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SMD code N20 in SOT-343

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.

1 part in SOT-343 is printed N20

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • DA227SOT-353Switching diode, JSCJSwitching diodeJSCJ
    What it is
    Switching diode
    Maker
    JSCJ
    Package
    SOT-353
    Pins
    5
    Details
    Switching diode, 80 V, 100 mA
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: Silicon diode.

    Datasheetfor DA227, opens in a new tab
  • 2 more parts have no package on record. Nothing rules them out, so they stay.
    • LN3420DT2AGN-channel MOSFET, LRCN-channel MOSFETLRC
      What it is
      N-channel MOSFET
      Maker
      LRC
      Package
      Not recorded
      Pins
      Not recorded
      Details
      MOSFET, N-Channel, VDSS 30 V, VGS 20 V
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: N-channel MOSFET.

      Datasheetfor LN3420DT2AG, opens in a new tab
    • LDTC143TET1GDigital transistor (NPN, resistors built in), LRCDigital transistor (NPN, resistors built in)LRC
      What it is
      Digital transistor (NPN, resistors built in)
      Maker
      LRC
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Digital transistor (bias resistors built in), NPN, IC 100 mA, VCEO 50 V
      Source
      An older or alternative marking, from a published code list

      Is it dead? The meter test is below: Digital transistor.

      Datasheetfor LDTC143TET1G, opens in a new tab

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.

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.

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.

Printed with a code easy to misread as N20

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 N20

For a marking with its end worn or burnt off. Each code has a page of its own.

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