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SMD code R20

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.

R20 on a chip resistor

0.2 Ω

0.2 Ω resistor

The R stands in for the decimal point, which is how sub-ohm and fractional values are printed. The same marking also reads as 0.2 µH on an inductor or 0.2 pF on a capacitor, and nothing in the code says which; the body of the part does.

The same characters on another part

  • 0.2 µH inductor
  • 0.2 pF capacitor

Check it with a meter

Lift one end and measure across it. A good one reads 0.2 Ω. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 0.2 Ω on the board is a fault. Open, or well above 0.2 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 0.2 Ω. A burnt resistor usually means the part it feeds drew too much, so find that before fitting a new one.

On a transistor or diode body (SOT-23, SOT-323, SOT-353), R20 is a part code instead. Those parts are listed below.

2 parts are printed R20

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.

3 pins. What differs:

  • CJ3420SOT-23N-channel MOSFET, JSCJ
    What it is
    N-channel MOSFET
    Maker
    JSCJ
    Package
    SOT-23
    Pins
    3
    Details
    MOSFET, N-channel, 20 V, 6 A
    Source
    From the manufacturer's datasheet

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

    Datasheetfor CJ3420, opens in a new tab
  • REF3320AIDCKSOT-323Voltage reference, Texas Instruments
    What it is
    Voltage reference
    Maker
    Texas Instruments
    Package
    SOT-323
    Pins
    3
    Details
    3.9μA, SC70-3, SOT-23-3, and UQFN-8, 30ppm/°C Drift Voltage Reference
    Source
    From the manufacturer's datasheet

    Is it dead? The meter test is below: Integrated circuit.

    Datasheetfor REF3320AIDCK, 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.

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.

Integrated circuit

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.

Printed with a code easy to misread as R20

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

Open this in the search to correct a character or try another package.