TIP127 Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

TO-220AB

Physical pin numbers3 pins

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TIP127 pin functions and connections
Signal	Type	Function & connection
B	Base	Input of the first PNP in the Darlington pair. Connection guidance Sink 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 guidance Connect 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 guidance Connect to +12 V in the example. Front-facing TO-220: B1, C2, E3. The DPAK tab is collector pad 2.

Two documented onsemi selections

Manufacturer-referenced values5 parameters

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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

Electrical values below are magnitudes; PNP voltage and current signs reverse.

Individual stress limits, not simultaneous targets

Manufacturer-referenced values5 parameters

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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

Do not infer allowable load power from collector-current ratings.

TC 25°C; pulse ≤300 µs, duty ≤2%

Manufacturer-referenced values7 parameters

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Gain does not make the on-state voltage drop disappear.

TC 25°C; separate SMD reference

Manufacturer-referenced values8 parameters

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Read each test condition before comparing the SMD and through-hole variants.

Case and ambient limits are different

Manufacturer-referenced values6 parameters

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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

The model artwork is not a heatsink rating.

Explicit illustrative assumptions

Manufacturer-referenced values7 parameters

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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

Use a real level-shifted or buffered control stage; do not connect a low-voltage GPIO directly.