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SMD code 40W

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.

2 parts are printed 40W

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

all NXP. What differs:

  • BAS40XYSOT-363Schottky diode, 6 pinsSchottky diodeSOT-3636 pins
    What it is
    Schottky diode
    Maker
    NXP
    Package
    SOT-363
    Pins
    6
    Source
    Published code list

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

  • PMBFJ110SOT-23JFET, 3 pinsJFETSOT-233 pins
    What it is
    JFET
    Maker
    NXP
    Package
    SOT-23
    Pins
    3
    Details
    N-channel junction FETs
    Source
    An older or alternative marking, from a published code list

    Is it dead? The meter test is below: JFET.

    Datasheetfor PMBFJ110, 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.

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.

JFET

Ohms range for drain to source, diode range for the gate, part lifted.

Working, it reads

Drain to source conducts both ways at a few hundred ohms, depending on the part, and some meters beep on it. The gate reads one junction to drain and to source, about 0.6 to 0.7 V, and open the other way.

Dead, it reads

  • The gate the same both ways to drain or source, near 0 V with a continuous beep: gate shorted.
  • Drain to source open: the channel has 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:
Drain to source resistance varies from part to part. An identical part elsewhere on the board shows what is normal.
Watch for:
A good channel can beep like a short between drain and source. That is normal; the gate junction says whether it has failed.

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 40W

One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.

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