Real View
TIP127PNP Darlington power transistor
High gain for a positive-side load switch.
TIP127 is a PNP Darlington power transistor. Two transistors share a collector, with the first emitter driving the second base for high overall current gain. Internal base-emitter resistors provide discharge paths, while the external circuit controls the operating point. The selected onsemi TIP127G uses a TO-220 body with base 1, collector 2 and emitter 3. MJD127T4G is the manufacturer’s documented DPAK replacement family: its physical layout, thermal limits, leakage and electrical test points must be checked separately. The example switches a 12 V resistor load from the positive side. A source-referenced buffered driver sinks base current to turn on and returns to the emitter voltage to turn off. The displayed currents and power are calculations using stated voltage-drop assumptions.
3Physical pins
TIP127GTO-220AB
Manufacturer-referencedonsemi
Pin diagram
Select a pin to explore its connection
Highlight
TIP127GTO-220ABFront view · B1, C2, E3 · tab = C
MJD127T4GDPAKTop view · B1, collector pad 2, E3
Click a lead or use the arrow keys. Front view · B1, C2, E3 · tab = C
PIN 1 · Base / drive
BaseB
Function
Input of the first PNP in the Darlington pair.
How to connect
Sink base current through 1 kΩ; connect a 10 kΩ return from base to emitter.
Electrical note
The example driver selects 12 V for off and 7 V for on. A 3.3 V GPIO cannot directly turn off this 12 V high-side stage.
PIN 2 · Collector / load
CollectorC
Function
Common collector of the two internal PNP transistors.
How to connect
Connect the load between collector and ground.
Electrical note
The metal tab is electrically collector; keep heatsinks at a compatible potential or insulate them.
PIN 3 · Supply
EmitterE
Function
Positive supply and base-drive reference.
How to connect
Connect to +12 V in the example.
Electrical note
Front-facing TO-220: B1, C2, E3. The DPAK tab is collector pad 2.
Key specifications
The two-stage PNP connection switches from the positive rail. Match the drive to emitter voltage, budget base current, and use the selected package’s safe operating area and thermal limits.
Collector limit−100 V · absolute VCEO
TO-220 current limit5 A magnitude · absolute
DC gain minimum1000 At specified test points
Junction limit150 °C · maximum
Package details
TIP127G · TO-220AB
| Property | Details |
|---|---|
| Manufacturer | onsemi |
| Part number | TIP127G |
| Package | TO-220AB |
| Connections | 3 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | 221A style 1 |
| Thermal reference | 65 W at case 25°C; 2 W at ambient 25°C |
Device and package scope
Two documented onsemi selections
Manufacturer specifications 5 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Through-hole | TIP127G · TO-220AB | TIP120/D Rev. 10, June 2024 |
| Surface-mount | MJD127T4G · DPAK | MJD122/D Rev. 16, April 2026 |
| Connection | PNP Darlington · B1, C2, E3 | Metal tab/contact 4 is also collector |
| Construction | Two stages with internal shunt resistors | Approximately 8 kΩ / 120 Ω shown for TIP127 |
| SMD relationship | Documented replacement family | Different ratings and test points; not a footprint-compatible substitute |
No specifications match. Try a parameter name or a unit.
Electrical values below are magnitudes; PNP voltage and current signs reverse.
Absolute limits by package
Individual stress limits, not simultaneous targets
Manufacturer specifications 5 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Collector-emitter / collector-base | 100 / 100 V | Both selections |
| Emitter-base / base current | 5 V / 120 mA | Both selections |
| TO-220 DC / peak collector | 5 / 8 A | Thermal and SOA restrictions apply |
| DPAK DC / peak collector | 8 / 16 A | Different package and pulse conditions |
| Junction / storage | −65 to +150°C | Both selections |
No specifications match. Try a parameter name or a unit.
Do not infer allowable load power from collector-current ratings.
TIP127 electrical characteristics
TC 25°C; pulse ≤300 µs, duty ≤2%
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| hFE minimum | 1000 | IC 0.5 A or 3 A; VCE 3 V |
| VCE(sat) maximum | 2 V / 4 V | IC 3 A / 5 A; IB 12 mA / 20 mA |
| VBE(on) maximum | 2.5 V | IC 3 A; VCE 3 V |
| ICEO maximum | 0.5 mA | VCE 50 V; base open |
| ICBO / IEBO maximum | 0.2 / 2 mA | VCB 100 V / VBE 5 V |
| Small-signal gain minimum | 4 | IC 3 A; VCE 4 V; 1 MHz |
| Output capacitance maximum | 300 pF | PNP; VCB 10 V; 0.1 MHz |
No specifications match. Try a parameter name or a unit.
Gain does not make the on-state voltage drop disappear.
MJD127 electrical characteristics
TC 25°C; separate SMD reference
Manufacturer specifications 8 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| hFE | 1000–12000 at 4 A; ≥100 at 8 A | VCE 4 V |
| VCE(sat) maximum | 2 V / 4 V | IC 4 A / 8 A; IB 16 mA / 80 mA |
| VBE(on) maximum | 2.8 V | IC 4 A; VCE 4 V |
| VBE(sat) maximum | 4.5 V | IC 8 A; IB 80 mA; pulse ≤300 µs, duty ≤2% |
| ICEO / ICBO maximum | 10 / 10 µA | VCE 50 V / VCB 100 V |
| IEBO maximum | 2 mA | VBE 5 V; collector open |
| Small-signal gain minimum | 4 at 1 MHz; 300 at 1 kHz | IC 3 A; VCE 4 V |
| Output capacitance maximum | 300 pF | PNP; VCB 10 V; 0.1 MHz |
No specifications match. Try a parameter name or a unit.
Read each test condition before comparing the SMD and through-hole variants.
Thermal and safe operating area
Case and ambient limits are different
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 case / ambient power | 65 W / 2 W | At case / ambient 25°C; derate 0.52 / 0.016 W per °C |
| TO-220 RθJC / RθJA | 1.92 / 62.5°C/W | Maximum |
| DPAK case / ambient power | 20 W / 1.75 W | At 25°C; derate 0.16 / 0.014 W per °C |
| DPAK RθJC / RθJA | 6.25 / 71.4°C/W | Specified minimum land pattern |
| Safe operating area | Use the selected manufacturer curves | Second breakdown and pulse duration also matter |
| Inductive loads | Use a suitable external clamp | The pictured resistor does not store magnetic energy |
No specifications match. Try a parameter name or a unit.
The model artwork is not a heatsink rating.
Positive-side resistor-load switch
Explicit illustrative assumptions
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Emitter / collector load | +12 V / 100 Ω to ground | Use at least a 2 W resistor with thermal margin |
| Buffered driver | 12 V off; 7 V on | Must sink base current; referenced to the emitter supply |
| Base resistor / return | 1 kΩ / 10 kΩ | Return goes to emitter, not ground |
| Assumed drops | |VBE| 1.4 V; |VCE| 1 V | Teaching assumptions, not guaranteed test points |
| Device base current | 3.46 mA | (5−1.4)/1000−1.4/10000 |
| Collector / forced current ratio | 110 mA / 31.8 | (12−1)/100; IC/IB |
| Device / load loss | 0.115 W / 1.21 W | Includes base contribution |
No specifications match. Try a parameter name or a unit.
Use a real level-shifted or buffered control stage; do not connect a low-voltage GPIO directly.
Connections by function
Select a pin for its function, connection guidance and electrical notes.
Base / drive1 pin
Collector / load1 pin
Supply1 pin
Base / drive1 pin
Collector / load1 pin
Supply1 pin
TIP127 at a glance
Follow the labeled connections and functional stages
How it works
3 stages · Explore one step at a time
Sink base current
Pull the first PNP base below emitter through the resistor.
Drive the second stage
The first transistor drives the second; their collectors are common.
Return to off
Return base to emitter voltage and allow internal charge to discharge.
Step 1 of 3
TIP127 in a circuit
Emitter supply and base-drive reference remain explicit.
Connect it, step by step
Follow the component values and pin connections
Supply
Emitter pin 3 connects to +12 V; collector pin 2 feeds the load.
Drive
A 1 kΩ resistor limits the base current drawn by the buffered driver.
Return
10 kΩ returns base to emitter; the load and driver share ground.
Inside TIP127
Two PNP stages, common collector and internal discharge resistors.
Explore the circuit
Select a stage to see its role and connections
First PNP stage
Base current controls the first transistor.
Second PNP stage
The first emitter feeds the second base; both collectors are joined.
Internal return paths
TIP127’s reference shows approximately 8 kΩ and 120 Ω shunts; this is a functional schematic.
Selected packageTO-220ABTIP127G
Physical connections3 pinsPackage-specific numbering
Reference collection7 tables38 parameters & pin functions
Pin reference
Signal names, electrical functions and connection guidance
Physical pin numbers3 pins
Scroll within the table to see all columns and rows.
| Pin | Signal | Type | Function & connection |
|---|---|---|---|
| B | Base | Input of the first PNP in the Darlington pair.Connection guidanceSink base current through 1 kΩ; connect a 10 kΩ return from base to emitter. The example driver selects 12 V for off and 7 V for on. A 3.3 V GPIO cannot directly turn off this 12 V high-side stage. | |
| C | Collector | Common collector of the two internal PNP transistors.Connection guidanceConnect the load between collector and ground. The metal tab is electrically collector; keep heatsinks at a compatible potential or insulate them. | |
| E | Emitter | Positive supply and base-drive reference.Connection guidanceConnect to +12 V in the example. Front-facing TO-220: B1, C2, E3. The DPAK tab is collector pad 2. |
No pins match these filters. Try another signal name or reset the filters.
Device and package scope
Two documented onsemi selections
Manufacturer-referenced values5 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Through-hole | TIP127G · TO-220AB | TIP120/D Rev. 10, June 2024 |
| Surface-mount | MJD127T4G · DPAK | MJD122/D Rev. 16, April 2026 |
| Connection | PNP Darlington · B1, C2, E3 | Metal tab/contact 4 is also collector |
| Construction | Two stages with internal shunt resistors | Approximately 8 kΩ / 120 Ω shown for TIP127 |
| SMD relationship | Documented replacement family | Different ratings and test points; not a footprint-compatible substitute |
No specifications match. Try a parameter name or a unit.
Electrical values below are magnitudes; PNP voltage and current signs reverse.
Absolute limits by package
Individual stress limits, not simultaneous targets
Manufacturer-referenced values5 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Collector-emitter / collector-base | 100 / 100 V | Both selections |
| Emitter-base / base current | 5 V / 120 mA | Both selections |
| TO-220 DC / peak collector | 5 / 8 A | Thermal and SOA restrictions apply |
| DPAK DC / peak collector | 8 / 16 A | Different package and pulse conditions |
| Junction / storage | −65 to +150°C | Both selections |
No specifications match. Try a parameter name or a unit.
Do not infer allowable load power from collector-current ratings.
TIP127 electrical characteristics
TC 25°C; pulse ≤300 µs, duty ≤2%
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| hFE minimum | 1000 | IC 0.5 A or 3 A; VCE 3 V |
| VCE(sat) maximum | 2 V / 4 V | IC 3 A / 5 A; IB 12 mA / 20 mA |
| VBE(on) maximum | 2.5 V | IC 3 A; VCE 3 V |
| ICEO maximum | 0.5 mA | VCE 50 V; base open |
| ICBO / IEBO maximum | 0.2 / 2 mA | VCB 100 V / VBE 5 V |
| Small-signal gain minimum | 4 | IC 3 A; VCE 4 V; 1 MHz |
| Output capacitance maximum | 300 pF | PNP; VCB 10 V; 0.1 MHz |
No specifications match. Try a parameter name or a unit.
Gain does not make the on-state voltage drop disappear.
MJD127 electrical characteristics
TC 25°C; separate SMD reference
Manufacturer-referenced values8 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| hFE | 1000–12000 at 4 A; ≥100 at 8 A | VCE 4 V |
| VCE(sat) maximum | 2 V / 4 V | IC 4 A / 8 A; IB 16 mA / 80 mA |
| VBE(on) maximum | 2.8 V | IC 4 A; VCE 4 V |
| VBE(sat) maximum | 4.5 V | IC 8 A; IB 80 mA; pulse ≤300 µs, duty ≤2% |
| ICEO / ICBO maximum | 10 / 10 µA | VCE 50 V / VCB 100 V |
| IEBO maximum | 2 mA | VBE 5 V; collector open |
| Small-signal gain minimum | 4 at 1 MHz; 300 at 1 kHz | IC 3 A; VCE 4 V |
| Output capacitance maximum | 300 pF | PNP; VCB 10 V; 0.1 MHz |
No specifications match. Try a parameter name or a unit.
Read each test condition before comparing the SMD and through-hole variants.
Thermal and safe operating area
Case and ambient limits are different
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| TO-220 case / ambient power | 65 W / 2 W | At case / ambient 25°C; derate 0.52 / 0.016 W per °C |
| TO-220 RθJC / RθJA | 1.92 / 62.5°C/W | Maximum |
| DPAK case / ambient power | 20 W / 1.75 W | At 25°C; derate 0.16 / 0.014 W per °C |
| DPAK RθJC / RθJA | 6.25 / 71.4°C/W | Specified minimum land pattern |
| Safe operating area | Use the selected manufacturer curves | Second breakdown and pulse duration also matter |
| Inductive loads | Use a suitable external clamp | The pictured resistor does not store magnetic energy |
No specifications match. Try a parameter name or a unit.
The model artwork is not a heatsink rating.
Positive-side resistor-load switch
Explicit illustrative assumptions
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Emitter / collector load | +12 V / 100 Ω to ground | Use at least a 2 W resistor with thermal margin |
| Buffered driver | 12 V off; 7 V on | Must sink base current; referenced to the emitter supply |
| Base resistor / return | 1 kΩ / 10 kΩ | Return goes to emitter, not ground |
| Assumed drops | |VBE| 1.4 V; |VCE| 1 V | Teaching assumptions, not guaranteed test points |
| Device base current | 3.46 mA | (5−1.4)/1000−1.4/10000 |
| Collector / forced current ratio | 110 mA / 31.8 | (12−1)/100; IC/IB |
| Device / load loss | 0.115 W / 1.21 W | Includes base contribution |
No specifications match. Try a parameter name or a unit.
Use a real level-shifted or buffered control stage; do not connect a low-voltage GPIO directly.
No matching rowsTry a pin name, parameter, unit or test condition, or reset the filters.
Positive-side load switches
Switch modest DC loads with emitter-referenced base drive.
Manufacturer application guideComplementary output stages
Pair with an appropriate NPN Darlington using explicit bias and thermal design.
Manufacturer application guideLow-speed power control
Use high gain where the on-state voltage drop is acceptable.
Manufacturer application guideTake it into ProTech
Find TIP127 in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech