Real View
MJ2955PNP metal-can power transistor
A controlled current path, with every terminal identified.
MJ2955 is a PNP power transistor in a metal TO-204AA (TO-3) package. The two insulated leads are base 1 and emitter 2; the metal case itself is collector. Both mounting contacts share that collector connection. The 15 A collector rating is an absolute limit. Usable current also depends on base drive, safe operating area and heat removal. The pin diagram explicitly shows the bottom view, while the authored PCB pattern uses the top view. The example switches a modest 12 V, 100 Ω load with a buffered driver. Calculated readings assume 0.8 V base-emitter and 0.2 V collector-emitter magnitudes, not guaranteed voltage drops. Only the verified metal package is offered.
3Terminals · 2 leads + case
MJ2955TO-204AA (TO-3)
Manufacturer-referencedonsemi
Pin diagram
Select a pin to explore its connection
Highlight
MJ2955TO-204AA (TO-3)Bottom view · B1, E2 · case C3
Click a lead or use the arrow keys. Bottom view · B1, E2 · case C3
PIN 1 · Base / drive
BaseB
Function
Current-driven control junction.
How to connect
Use the example’s 330 Ω series drive and 10 kΩ base-emitter return.
Electrical note
Bottom view of CASE 1-07: base 1 below emitter 2, offset toward the left mounting hole.
PIN 2 · Supply
EmitterE
Function
Reference terminal for base drive.
How to connect
Connect to +12 V.
Electrical note
Bottom view of CASE 1-07: base 1 below emitter 2, offset toward the left mounting hole.
PIN 3 · Collector / load
CollectorC
Function
The metal case is the collector; there is no third wire lead.
How to connect
Connect to the 100 Ω load above ground.
Electrical note
Both mounting contacts belong to collector. Insulate the heatsink when required.
Key specifications
The mounting case is electrically live. The two silver leads are base and emitter; do not assume the case is ground.
Collector limit60 V · VCEO magnitude
Collector limit15 A · absolute
Case-cooled power115 W · case 25°C
Electrical terminals3 Two leads + collector case
Package details
MJ2955 · TO-204AA (TO-3)
| Property | Details |
|---|---|
| Manufacturer | onsemi |
| Part number | MJ2955 |
| Package | TO-204AA (TO-3) |
| Connections | 3 pins |
| Mounting | Through-hole |
| Lead pitch | 10.92 mm lead spacing |
| Package code | CASE 1-07 |
| Thermal reference | 115 W at case 25°C; heatsink required |
Device and package
Selected manufacturer reference
Manufacturer specifications 4 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Device | MJ2955 | onsemi complementary power transistor family |
| Polarity | PNP | Voltages and currents below use magnitudes |
| Physical connection | B1 · E2 · case C3 | Two insulated TO-3 leads; case is collector |
| Package | TO-204AA (TO-3) | CASE 1-07, style 1 |
No specifications match. Try a parameter name or a unit.
No unverified SMD substitute is selected.
Absolute limits
Do not combine maxima into one operating point
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Collector-emitter VCEO | 60 V | Open base |
| Collector-emitter VCER | 70 V | 100 Ω base-emitter resistor |
| Collector-base voltage | 100 V | Absolute maximum |
| Emitter-base reverse voltage | 7 V | Absolute maximum |
| Collector / base current | 15 A / 7 A | Absolute maximum |
| Dissipation | 115 W at case 25°C | Derate 0.657 W/°C |
| Junction / storage | −65 to +200°C | Absolute limits |
No specifications match. Try a parameter name or a unit.
Apply the manufacturer safe operating area.
Electrical characteristics
25°C and stated manufacturer conditions
Manufacturer specifications 5 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| DC gain at 4 A | 20–70 | VCE magnitude 4 V |
| DC gain at 10 A | 5 minimum | VCE magnitude 4 V |
| Saturation at 4 A / 400 mA base | 1.1 V maximum | Case 25°C |
| Saturation at 10 A / 3.3 A base | 3 V maximum | Case 25°C |
| Base-emitter on voltage | 1.5 V maximum | IC magnitude 4 A; VCE magnitude 4 V |
No specifications match. Try a parameter name or a unit.
PNP test currents and voltages are negative in the source; magnitudes are shown.
Thermal and package data
Case and ambient conditions differ
Manufacturer specifications 4 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Junction-to-case | 1.52°C/W maximum | Controlled case |
| Mounting centres | 30.15 mm | Collector case |
| Base/emitter spacing | 10.92 mm | CASE 1-07 |
| Lead diameter | 0.97–1.09 mm | Two insulated leads |
No specifications match. Try a parameter name or a unit.
The authored footprint is a starting pattern, not a manufacturer land recommendation.
Calculated switch readings
Explicit low-current teaching assumptions
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply and load | 12 V / 100 Ω ≥3 W | Resistive load |
| Buffered driver | 12 V off / 7 V on | 330 Ω base resistor |
| Base-emitter return | 10 kΩ | Defined off state |
| Assumed junction drops | |VBE| 0.8 V / |VCE| 0.2 V | Illustrative only |
| Collector / base current | 118 mA / 12.65 mA | Includes base-return current |
| Device / load power | 33.7 mW / 1.392 W | Includes base-emitter input power |
No specifications match. Try a parameter name or a unit.
Do not infer high-current capability from this small example.
Connections by function
Select a pin for its function, connection guidance and electrical notes.
Base / drive1 pin
Supply1 pin
Collector / load1 pin
MJ2955 at a glance
Follow the labeled connections and functional stages
How it works
3 stages · Explore one step at a time
Drive the base
Pull base below emitter through the resistor. The driver must return to +12 V to turn off.
Control current
Conventional current enters emitter and leaves collector.
Respect heat and voltage
Check safe operating area, drive current and cooling together; a current rating is not a guaranteed operating point.
Step 1 of 3
MJ2955 in a circuit
A modest resistor load with explicit buffered base drive.
Connect it, step by step
Follow the component values and pin connections
Drive the base
Pull base below emitter through the resistor. The driver must return to +12 V to turn off.
Control current
Conventional current enters emitter and leaves collector.
Respect heat and voltage
Check safe operating area, drive current and cooling together; a current rating is not a guaranteed operating point.
Inside MJ2955
Compact functional cutaway inside the metal package.
Explore the circuit
Select a stage to see its role and connections
Drive the base
Pull base below emitter through the resistor. The driver must return to +12 V to turn off.
Control current
Conventional current enters emitter and leaves collector.
Respect heat and voltage
Check safe operating area, drive current and cooling together; a current rating is not a guaranteed operating point.
Selected packageTO-204AA (TO-3)MJ2955
Physical connections3 pinsPackage-specific numbering
Reference collection6 tables26 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 | Current-driven control junction.Connection guidanceUse the example’s 330 Ω series drive and 10 kΩ base-emitter return. Bottom view of CASE 1-07: base 1 below emitter 2, offset toward the left mounting hole. | |
| E | Emitter | Reference terminal for base drive.Connection guidanceConnect to +12 V. Bottom view of CASE 1-07: base 1 below emitter 2, offset toward the left mounting hole. | |
| C | Collector | The metal case is the collector; there is no third wire lead.Connection guidanceConnect to the 100 Ω load above ground. Both mounting contacts belong to collector. Insulate the heatsink when required. |
No pins match these filters. Try another signal name or reset the filters.
Device and package
Selected manufacturer reference
Manufacturer-referenced values4 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Device | MJ2955 | onsemi complementary power transistor family |
| Polarity | PNP | Voltages and currents below use magnitudes |
| Physical connection | B1 · E2 · case C3 | Two insulated TO-3 leads; case is collector |
| Package | TO-204AA (TO-3) | CASE 1-07, style 1 |
No specifications match. Try a parameter name or a unit.
No unverified SMD substitute is selected.
Absolute limits
Do not combine maxima into one operating point
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Collector-emitter VCEO | 60 V | Open base |
| Collector-emitter VCER | 70 V | 100 Ω base-emitter resistor |
| Collector-base voltage | 100 V | Absolute maximum |
| Emitter-base reverse voltage | 7 V | Absolute maximum |
| Collector / base current | 15 A / 7 A | Absolute maximum |
| Dissipation | 115 W at case 25°C | Derate 0.657 W/°C |
| Junction / storage | −65 to +200°C | Absolute limits |
No specifications match. Try a parameter name or a unit.
Apply the manufacturer safe operating area.
Electrical characteristics
25°C and stated manufacturer conditions
Manufacturer-referenced values5 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| DC gain at 4 A | 20–70 | VCE magnitude 4 V |
| DC gain at 10 A | 5 minimum | VCE magnitude 4 V |
| Saturation at 4 A / 400 mA base | 1.1 V maximum | Case 25°C |
| Saturation at 10 A / 3.3 A base | 3 V maximum | Case 25°C |
| Base-emitter on voltage | 1.5 V maximum | IC magnitude 4 A; VCE magnitude 4 V |
No specifications match. Try a parameter name or a unit.
PNP test currents and voltages are negative in the source; magnitudes are shown.
Thermal and package data
Case and ambient conditions differ
Manufacturer-referenced values4 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Junction-to-case | 1.52°C/W maximum | Controlled case |
| Mounting centres | 30.15 mm | Collector case |
| Base/emitter spacing | 10.92 mm | CASE 1-07 |
| Lead diameter | 0.97–1.09 mm | Two insulated leads |
No specifications match. Try a parameter name or a unit.
The authored footprint is a starting pattern, not a manufacturer land recommendation.
Calculated switch readings
Explicit low-current teaching assumptions
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply and load | 12 V / 100 Ω ≥3 W | Resistive load |
| Buffered driver | 12 V off / 7 V on | 330 Ω base resistor |
| Base-emitter return | 10 kΩ | Defined off state |
| Assumed junction drops | |VBE| 0.8 V / |VCE| 0.2 V | Illustrative only |
| Collector / base current | 118 mA / 12.65 mA | Includes base-return current |
| Device / load power | 33.7 mW / 1.392 W | Includes base-emitter input power |
No specifications match. Try a parameter name or a unit.
Do not infer high-current capability from this small example.
No matching rowsTry a pin name, parameter, unit or test condition, or reset the filters.
Switching
Control loads within the electrical and thermal ratings.
Manufacturer application guideAmplification
Choose bias and a safe operating point rather than assuming saturation behavior.
Manufacturer application guidePackage replacement
Match the exact voltage grade, polarity, lead order and case connection before substituting a part.
Manufacturer application guideTake it into ProTech
Find MJ2955 in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech