MJ3055 - NPN 60V 10A Power Transistor TO-3 | Seme LAB
N.º de pieza: MJ3055 ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $0.78 | $0,78 |
| 10 | $0.71 | $7,10 |
| 100 | $0.63 | $63,00 |
| 500 | $0.56 | $280,00 |
| 1.000 | $0.49 | $490,00 |
MJ3055 Descripción general
A power BJT (bipolar junction transistor) is a current-controlled semiconductor switch or amplifier that sits at the top of the discrete transistor hierarchy: transistor -> bipolar junction transistor (BJT) -> power transistor -> power semiconductor device. Unlike MOSFETs, BJTs require base drive current proportional to collector current, but they offer ruggedness, low saturation behavior at moderate currents, and proven reliability in high-vibration and high-temperature environments.
Key features of the MJ3055 include a 60V VCEO breakdown rating, 10A maximum collector current, and the hermetically sealed TO-3 metal package, which provides superior thermal path (collector bonded to the case) and environmental sealing compared with plastic TO-220 alternatives. The hermetic version, produced by Seme LAB, can additionally be screened to BS, CECC and JAN, JANTX, JANTXV and JANS specification requirements, which is significant for military and aerospace procurement.
Electrically, the MJ3055 follows the industry-standard 3055 NPN power transistor architecture: a single-diffused silicon NPN die optimized for general-purpose amplification and switching, with a PNP complement (MJ2955) available for push-pull audio output designs. Transition frequency is in the low-MHz range, adequate for audio and low-frequency switching but not for high-speed converters.
Typical applications include linear bench power supplies, series-pass regulators, class-AB audio amplifier output stages, motor and relay drivers, and DC-DC converter prototypes where the 10A current rating and metal-can thermal performance are beneficial.
When designing with the MJ3055, mount the TO-3 can to a heatsink with insulating hardware and verify power dissipation against thermal resistance; base drive current must be budgeted at roughly 1/10th to 1/20th of collector current for hard saturation.
This page synthesizes verified distributor pricing, drop-in alternatives, cross-reference data, and practical design notes not found in the manufacturer shortform datasheet.
Alternativas directas para MJ3055 — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con MJ3055 (mismo factor de forma y huella) — difiere en Mounting Type, Package, Polarity.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
2N3055
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
MJ15015
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
MJ2955
✅ Sustitución directa✓ En stock
$1.4 / unidad
Ver hoja de datos →MJ3055 Valores máximos y características eléctricas
| Polarity | NPN |
| Collector-Emitter Breakdown Voltage (VCEO) | 60 V |
| Maximum Collector Current (IC) | 10 A |
| Encapsulado | TO-3 (hermetically sealed metal can) |
| Technology | Bipolar (BJT), silicon NPN |
| Tipo de montaje | Through Hole |
| Hermetic Sealing | Yes (metal can) |
| Screening Options | BS, CECC, JAN, JANTX, JANTXV, JANS (per Seme LAB) |
| Complementary PNP Type | MJ2955 |
| Typical Applications | General-purpose amplifier and switching |
Configuración de pines de MJ3055
| Pin 1 | Base — Base control terminal (drive current input) |
| Pin 2 | Emitter — Emitter terminal (current output / common) |
| Pin 3 | Collector (Case) — Collector terminal, connected internally to the TO-3 metal can for heatsink mounting |
Área de funcionamiento seguro (indicative - verify with vendor full datasheet)
Aplicaciones típicas
MJ3055 es adecuado para 6 aplicacións: Linear Power Supply Series-Pass Regulator, Class-AB Audio Amplifier Output Stage, DC Motor and Relay Driver, Military and Aerospace Power Switching, Battery Charger and Welder-Style High-Current Control, Vintage and Service/Repair Equipment Maintenance.
Linear Power Supply Series-Pass Regulator
The MJ3055 excels as a series-pass element in linear bench and embedded power supplies. Its 60V VCEO accommodates rectified input rails up to roughly 50V with margin, and its 10A collector current rating supports multi-amp outputs without paralleling. The TO-3 metal can bonds the collector directly to the case, giving a very low case-to-heatsink thermal resistance, so dissipation of tens of watts is manageable with a modest heatsink and forced airflow. In a typical NPN pass-transistor regulator, the MJ3055 operates in the linear region with the error amplifier driving the base; budget base drive of about 0.5-1A at full load for hFE in the 20-70 range, or use a driver transistor stage. Compared with a plastic TO-220 part, the hermetic metal can also improves reliability in humid or thermally cycling environments.
Recomendado
Class-AB Audio Amplifier Output Stage
The classic MJ3055/MJ2955 complementary pair remains a staple of discrete class-AB audio power amplifiers. With 60V VCEO, the pair supports supply rails up to about +/-28V, delivering 30-50W into 4-8 ohm loads; the 10A IC rating comfortably handles low-impedance speaker current peaks. The TO-3 metal-can thermal path allows simple chassis-mounted heatsinking, and the low transition frequency (MHz class) inherently rolls off high-frequency gain, easing stability compensation in audio bandwidth designs. Bias the output pair with a Vbe multiplier and emitter resistors of 0.22-0.47 ohm for thermal stability. The hermetic MJ3055 variant adds moisture immunity for amplifiers operating in harsh or marine environments where plastic-packaged outputs degrade over time.
Recomendado
DC Motor and Relay Driver
For driving DC motors, solenoids, and heavy relays, the MJ3055 provides a rugged 10A switch with generous surge capability typical of single-diffused power BJTs. In low-side switch configuration, the load connects between the supply rail and the collector (case), simplifying heatsink mounting at chassis potential. Base drive current should be sized at roughly 1/10 to 1/20 of the load current for hard saturation, limiting on-state power dissipation. Note the device's low fT is irrelevant at DC and relay speeds. Always include a flyback (freewheeling) diode across inductive loads and verify the 60V VCEO is not exceeded by inductive kickback - a clamp or snubber is recommended when switching solenoids or motor windings.
Recomendado
Military and Aerospace Power Switching
The Seme LAB MJ3055 is manufactured as a bipolar NPN device in a hermetically sealed TO-3 metal package, and per the manufacturer all Semelab hermetically sealed products can be processed in accordance with BS, CECC and JAN, JANTX, JANTXV and JANS specification requirements. This makes the part directly procurable for defense and space programs where qualified hermetic discrete semiconductors are mandated. The metal can withstands thermal vacuum, humidity, and salt-fog environments that degrade plastic encapsulants, while screening removes infant-mortality failures. Designers should derate collector current and power dissipation per program reliability guidelines and use qualified mounting hardware to preserve the hermetic seal during installation.
Recomendado
Battery Charger and Welder-Style High-Current Control
Battery chargers, plating supplies, and light spot-welder controls benefit from the MJ3055's 10A continuous rating and rugged SOA at low collector-emitter voltages. As a series regulator or chopper in these high-current, low-frequency applications, the transistor handles repeated current surges from discharged battery loads. The TO-3 case allows direct bolting to a large chassis heatsink, and its collector-to-case construction means the heatsink can double as the output terminal when isolated appropriately. For duty-cycle control, drive the base from a Darlington or MOSFET buffer to reduce drive power at 10A loads. Verify SOA at your worst-case VCE and pulse duration using the vendor full datasheet curves rather than relying on continuous ratings alone.
Recomendado
Vintage and Service/Repair Equipment Maintenance
The MJ3055 is one of the most commonly requested parts for repairing legacy power supplies, amplifiers, and industrial controls from the 1970s-1990s that were designed around TO-3 NPN output devices. Because the 3055 pinout and TO-3 mechanical outline were industry-standard, the MJ3055 (or its 2N3055 equivalent) drops directly onto original mica insulators and mounting clamps without rework. For service technicians, keeping MJ3055/MJ2955 pairs on hand resolves most TO-3 NPN/PNP output-stage failures. At approximately $0.77 per unit as of 2026-10-20 (LCSC, SPTECH), replacing both output devices as a matched pair after a failure is inexpensive insurance against the surviving device having been stressed.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para MJ3055 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | 2N3055 | MJ15015 | MJ2955 |
|---|---|---|---|---|
| Package | TO-3 hermetic metal can | TO-3 metal can - same | TO-3 metal can - same | TO-3 metal can - same |
| Brand | Seme LAB (hermetic; SPTECH commercial) | onsemi / multiple | onsemi | onsemi / multiple |
| Polarity | NPN | NPN | NPN | PNP |
| VCEO | 60 V | 60 V | Higher than 60 V (see vendor datasheet) | 60 V |
| Collector Current (IC) | 10 A | 10 A | 10 A class (see vendor datasheet) | 10 A |
| Approx. Unit Price (qty 1) | $0.78 (as of 2026-10-20, LCSC) | Similar (~$0.5-1.5) | ~3x higher (per cross-reference sources) | Similar (~$0.5-1.5) |
| Typical Use | Pass regulator, audio output, power switch | Identical applications - direct substitute | Higher-voltage output stages | PNP half of push-pull output pair |
Diferenciadores clave
- Hermetic sealed TO-3 metal can with military screening (frente a 2N3055)
- Identical footprint and ratings to industry-standard 2N3055 (frente a 2N3055)
- Cost advantage over upgraded TO-3 devices (frente a MJ15015)
Notas de diseño
The TO-3 collector is bonded to the metal case, so the heatsink becomes the electrical collector terminal. Mount with a mica or silicone insulator and thermal compound, and use a shoulder washer to isolate the mounting screw. Estimated: at 5A average with 3V VCE(sat)-class conduction in switching use, dissipation is roughly 15W; in linear pass operation with 15V across the device at 3A, dissipation reaches 45W - size the heatsink so case temperature stays below about 100C. Verify theta_JC against your vendor's full datasheet, as shortform data omits it.
Do not exceed the 60V VCEO rating: inductive loads (relays, motors, audio output transformers) can generate flyback spikes well above the supply rail. Always fit a freewheeling diode or RC snubber across inductive elements. Additionally, power BJTs have a secondary breakdown region in the SOA - high voltage AND high current simultaneously are more restrictive than either alone, so check the vendor SOA curves rather than extrapolating from the 10A/60V maximums.
The TO-3 is a through-hole metal-can device: plan mounting holes (approximately two holes on ~10.9mm centers plus a case tab) in the PCB or chassis, and keep base and emitter lead lengths short to limit parasitic oscillation. If the device oscillates in emitter-follower or audio service, add a small base stopper resistor (2.2-10 ohm) placed directly at the base pin. Maintain adequate copper area or bus wire for 10A collector/emitter currents.
Información de cumplimiento
RoHS/REACH status not stated in available datasheet excerpts; hermetic screened military parts may carry RoHS exemptions. Verify with the specific vendor (Seme LAB for screened, SPTECH for commercial).
