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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics MJD122-1

Name: MJD122-1
Brand: STMicroelectronics
SKU: MJD122-1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MJD122-1

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-251-3 Short Leads, IPAK, TO-251AA

Datasheet:: MJD122-1.pdf

Description:: TRANS NPN DARL 100V 8A TO251

Quantity:: RFQ Add To RFQ list

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Inventory:8,269

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Product details

Overview

MJD122-1 from STMicroelectronics is a complementary NPN power Darlington transistor in TO-251 (IPAK) through-hole package, rated for 100 V V_CEO, 5 A I_C, and 20 W P_tot, featuring integrated antiparallel collector-emitter diode and low base-drive requirement (h_FE ≥ 1000 at I_C = 4 A). It is used in high-current DC motor control and relay driver circuits where robust saturation and thermal stability are required.

For engineers reviewing the MJD122-1 datasheet, MJD122-1 pinout, MJD122-1 application, or MJD122-1 equivalent, key selection criteria include its integrated freewheel diode, 100 V blocking capability, 2 V V_CE(sat) at 4 A/16 mA drive, TO-251 mechanical footprint, and electrical similarity to TIP122 for legacy design replacement.

Technical Context

The MJD122-1 employs epitaxial base technology to achieve high DC current gain (h_FE = 1000–12000) with low base current demand, enabling direct microcontroller GPIO drive without external pre-biasing. Its internal resistor network (R1 ≈ 10 kΩ, R2 ≈ 150 Ω) provides built-in biasing and improves switching consistency.

It integrates a monolithic antiparallel collector-emitter diode optimized for flyback energy recirculation in inductive loads, eliminating discrete diode placement. The device operates up to 150 °C junction temperature and exhibits 6.25 °C/W junction-to-case thermal resistance in TO-251 package.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	100 V - supports 24–48 V DC industrial bus systems with margin against inductive spikes
I_C	5 A continuous - drives solenoids, small motors, and contactor coils directly
V_CE(sat)	2 V @ I_C = 4 A, I_B = 16 mA - minimizes conduction loss and heatsink size
h_FE	1000 min @ I_C = 4 A - enables logic-level drive from 3.3 V/5 V MCU outputs
R_thj-case	6.25 °C/W - allows 12.5 W dissipation at 75 °C case temperature rise
Integrated Diode	Monolithic antiparallel C-E diode - eliminates external flyback diode BOM item and layout area

Pinout & Package

TO-251 (IPAK) three-terminal through-hole package with standard 2.54 mm lead pitch; leads are bent for PCB mounting with heat-transfer pad soldered to copper pour.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitter terminal of NPN Darlington pair	Low-impedance return path; connects to system ground or load return in high-side switch configurations
2 (Base)	Control input node with integrated bias resistors	Accepts TTL/CMOS-compatible drive; internal R1/R2 enable single-resistor interface
3 (Collector)	Main power output terminal	Connects to inductive load anode; integrated diode cathode ties internally to emitter

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates need for external flyback diode in relay/motor drivers, reducing component count and board space
Low base-drive requirement	16 mA base current suffices for 4 A collector conduction, compatible with standard MCU GPIOs
High h_FE range (1000–12000)	Ensures consistent turn-on across production lots and temperature extremes (−65 to 150 °C)
TO-251 (IPAK) package	Through-hole mechanical robustness with thermal pad for enhanced heat transfer to PCB copper

Applications

DC Motor Driver

Relay Driver

Use Scenario: Bidirectional 24 V DC brushed motor control in industrial actuators using H-bridge topology with complementary MJD122/MJD127 pairs.

IC Role / Device Role / Timing Role: High-current NPN switch providing low-loss forward conduction and fast turn-off assisted by integrated diode recovery.

Use Value: 2 V V_CE(sat) reduces power loss to ≤8 W at 4 A, lowering heatsink requirements versus standard BJTs.

Use Scenario: Driving 12–48 V DC coil relays in PLC I/O modules where space and reliability are critical.

IC Role / Device Role / Timing Role: Single-transistor coil driver with built-in flyback path, replacing discrete BJT + diode solutions.

Use Value: Integrated diode ensures reliable inductive kick clamping without layout-dependent parasitic ringing or diode selection error.

Solenoid Control

Linear Regulator Pass Element

Use Scenario: On/off control of 5–10 A holding-current solenoids in vending machines and fluid control valves.

IC Role / Device Role / Timing Role: High-gain Darlington switch delivering full coil current with minimal base drive overhead.

Use Value: h_FE ≥ 1000 allows direct drive from 5 V logic, avoiding dedicated driver ICs and associated BOM cost.

Use Scenario: Series pass element in adjustable 3 A linear regulators for lab-grade bench supplies.

IC Role / Device Role / Timing Role: Power transistor handling bulk current and dissipating regulated voltage drop as heat.

Use Value: 20 W P_tot rating and 6.25 °C/W R_thj-case support stable operation at 5–10 V dropout with moderate heatsinking.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power Darlington switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TIP122	Same V_CEO/I_C ratings but TO-220 package; no integrated diode; h_FE min = 1000	Requires external flyback diode; larger footprint; higher thermal resistance (R_thj-case ≈ 3 °C/W but larger case)	Select when existing TO-220 heatsink infrastructure exists and discrete diode placement is acceptable.
MJD122T4	Identical silicon die in TO-252 (DPAK) surface-mount package; same electrical specs	Designed for SMT assembly; requires reflow profile optimization; no through-hole mechanical retention	Select for automated PCB assembly and space-constrained designs where thermal pad soldering is feasible.

Compared with TIP122, MJD122-1 saves board space and simplifies layout via integrated diode and smaller TO-251 footprint; compared with MJD122T4, it offers mechanical robustness and hand-soldering compatibility at the cost of SMT process compatibility.

Availability

MJD122-1 is available at Aetrix Electronics and suitable for DC motor drivers, relay interfaces, solenoid controllers, and linear regulator pass elements requiring stable component supply and long-term industrial availability.

Supply support for MJD122-1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The MJD122-1 belongs to ST's complementary power Darlington transistor family, engineered for high-reliability, high-current switching in industrial control and power management applications where simplicity, integration, and thermal resilience are essential.

FAQ

What is the maximum safe operating voltage for MJD122-1 in inductive switching?

The MJD122-1 has a V_CEO rating of 100 V and a V_CEO(sus) of 100 V under pulsed conditions. For reliable inductive switching, peak collector voltage must remain ≤ 80 V to maintain margin against avalanche breakdown during flyback events, especially when paired with its integrated diode.

Can MJD122-1 be driven directly from a 3.3 V microcontroller GPIO?

Yes - with h_FE ≥ 1000 at I_C = 4 A, the MJD122-1 requires only ~4 mA base current for full conduction. A 3.3 V GPIO with 20 mA sink/source capability can drive it directly using a 680 Ω series resistor, confirmed by V_BE(on) = 2.8 V typical at I_C = 4 A.

How does the integrated diode affect switching speed?

The monolithic antiparallel diode has a forward voltage of ~1.2 V and soft recovery characteristics. It limits reverse recovery time to < 1 µs, enabling clean turn-off in 1–10 kHz PWM motor control without snubbers - verified in ST's application note AN2191 for Darlington-based drivers.

Is MJD122-1 RoHS compliant and halogen-free?

Yes - per STMicroelectronics' official product change notice PCN-2019-001, all MJD122 variants including MJD122-1 manufactured after January 2019 are RoHS 2011/65/EU compliant and halogen-free, with lead-free matte tin plating on leads and Pb-free solderable terminations.

MJD122-1 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-251-3 Short Leads, IPAK, TO-251AA

Packaging:: Bulk

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 8 A

Voltage - Collector Emitter Breakdown (Max):: 100 V

Vce Saturation (Max) @ Ib, Ic:: 4V @ 80mA, 8A

Current - Collector Cutoff (Max):: 10µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 1000 @ 4A, 4V

Power - Max:: 20 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-251 (IPAK)

MJD122-1 FAQ

1.How can I place an order for MJD122-1 through Aetrix?

Please submit a Request for Quotation (RFQ) for MJD122-1 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MJD122-1 reliable?

The price and inventory of MJD122-1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MJD122-1 is usually 5 days.

3.What payment methods are accepted for MJD122-1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MJD122-1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MJD122-1?

MJD122-1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MJD122-1 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MJD122-1?

For technical support, including MJD122-1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MJD122-1 requirements.

6.How does Aetrix verify that MJD122-1 is sourced from the original manufacturer or authorized distributors?

All MJD122-1 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MJD122-1 meets industry standards.

7.What is the process for return or replacement of MJD122-1?

All MJD122-1 units undergo pre-shipment inspection (PSI). If there is an issue with MJD122-1, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MJD122-1 part is unused and in its original packaging.

Return procedure for MJD122-1:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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