SMD marking
R20in 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.
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.
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.
Not sure which one you have?
Answer up to 4 quick questions and these 8 parts are ranked, with a meter test that settles it. It works on a dead part too.
The only part printed R20 in this package in our tables
CJ3420
- 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?
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:
- 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.
Printed with a code easy to misread
These parts are printed with a character that is easy to misread as what you typed. The odd one out is marked on each.
Voltage reference, all SOT-23, 3 pins, all Texas Instruments.
LM4040DEM3-2.5printed R2DSOT-23
Printed R2D on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- LM4040-N/-Q1 Precision Micropower Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4040DEM3X-2.5printed R2DSOT-23
Printed R2D on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- LM4040-N/-Q1 Precision Micropower Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4040DIM3-2.5printed R2DSOT-23
Printed R2D on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- LM4040-N/-Q1 Precision Micropower Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4040DIM3X-2.5printed R2DSOT-23
Printed R2D on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- LM4040-N/-Q1 Precision Micropower Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4040QDEM3-2.5printed R2DSOT-23
Printed R2D on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- LM4040-N/-Q1 Precision Micropower Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4041QDEM3-ADJprinted RZDSOT-23
Printed RZD on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- Precision Micro Power Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
LM4041QDIM3-ADJprinted RZDSOT-23
Printed RZD on the part. Easy to misread as R20. Check that character with a loupe before you order anything.
- What it is
- Voltage reference
- Maker
- Texas Instruments
- Package
- SOT-23
- Pins
- 3
- Details
- Precision Micro Power Shunt Voltage Reference
- Source
- From the manufacturer's datasheet
Is it dead?
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.
Open this in the search to correct a character or try another package.