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

STMicroelectronics TIP122

Name: TIP122
Brand: STMicroelectronics
SKU: TIP122
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TIP122

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: TIP122.pdf

Description:: TRANS NPN DARL 100V 5A TO-220

Quantity:: RFQ Add To RFQ list

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Inventory:742

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Product details

Overview

TIP122 from STMicroelectronics is an NPN silicon Darlington power transistor in TO-220 package, designed for high-current linear and switching applications. It delivers 100 V V_CEO, 5 A continuous collector current, 65 W power dissipation at T_C ≤ 25°C, and features integrated base resistors (R1 = 7 kΩ, R2 = 70 Ω) enabling direct TTL/CMOS drive. It is commonly used in motor control, relay drivers, and lamp dimmers.

For engineers reviewing the TIP122 datasheet, TIP122 pinout, TIP122 application, or TIP122 equivalent, key selection criteria include its 100 V blocking capability, low 2 V V_CE(sat) at 3 A/12 mA drive, monolithic Darlington gain >1000, thermal resistance of 1.92 °C/W (junction-to-case), and compatibility with standard TO-220 heatsinking.

Technical Context

The TIP122 uses planar "base island" technology and a monolithic Darlington configuration-two cascaded NPN transistors on a single die-to achieve high DC current gain (h_FE ≥ 1000 at I_C = 0.5 A and 3 A) while maintaining low saturation voltage. Its internal base-emitter shunt resistor (R2) ensures reliable turn-off.

It operates with a maximum junction temperature of 150°C and exhibits stable gain across -40°C to 125°C. The device's safe operating area (SOA) supports pulsed currents up to 8 A, and its thermal resistance (R_thJC = 1.92 °C/W) enables efficient heat transfer to external heatsinks via the metal tab.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	100 V - Sustains 100 V collector-emitter voltage with base open; suitable for 72 V DC bus or 100 V peak AC line-switching circuits.
I_C (continuous)	5 A - Supports sustained load currents up to 5 A with proper heatsinking; enables driving solenoids, small motors, or LED arrays.
V_CE(sat)	2 V @ I_C = 3 A, I_B = 12 mA - Low saturation loss reduces power dissipation and self-heating during on-state operation.
h_FE	≥1000 @ I_C = 0.5 A, V_CE = 3 V - High gain allows microcontroller GPIOs to directly switch loads without external driver stages.
R_thJC	1.92 °C/W - Enables predictable junction temperature rise under load; 30°C rise at 15.6 W dissipation with minimal heatsink.
P_TOT	65 W @ T_C ≤ 25°C - Maximum power handling when case is actively cooled; derates linearly above 25°C ambient.

Pinout & Package

Package: TO-220 type H (metal tab connected to collector). Standard through-hole mounting with integral heatsink interface via tab.

Pin/Terminal	Circuit Role	Design Meaning
B (Pin 1)	Base	Control input; internally biased via 7 kΩ resistor to V_CC; accepts logic-level drive (TTL/CMOS compatible).
C (Pin 2 & Tab)	Collector	Main high-side current path; electrically connected to metal tab for direct heatsink attachment and thermal conduction.
E (Pin 3)	Emitter	Current return path; isolated from tab; connects to ground or low-side load reference.

Key Features

Feature	Design Value
Integrated base bias network	R1 = 7 kΩ pull-up + R2 = 70 Ω pull-down enables clean turn-on/turn-off without external resistors.
Low V_CE(sat)	2 V at 3 A reduces conduction losses by >40% vs. conventional power transistors at same current.
Monolithic Darlington structure	Single-die integration eliminates inter-device mismatch, improves thermal tracking, and enhances reliability vs. discrete pairs.
High SOA robustness	Supports 8 A pulsed current and resists secondary breakdown-critical for inductive load switching (e.g., relays, motors).

Applications

DC Motor Control

Relay Driver Circuit

Use Scenario: Bidirectional 24–48 V brushed DC motor control in industrial actuators and HVAC dampers.

IC Role / Device Role / Timing Role: High-side NPN switch controlling motor current path; driven by PWM signal from microcontroller.

Use Value: 100 V rating accommodates back-EMF spikes; 5 A rating supports motors up to ~200 W; low V_CE(sat) minimizes heat generation during PWM on-time.

Use Scenario: Driving 12–24 V coil relays in PLC I/O modules and building automation panels.

IC Role / Device Role / Timing Role: Single-transistor relay driver replacing discrete BJT + base resistor networks.

Use Value: Integrated R1/R2 eliminates two external components; 1000+ h_FE ensures full saturation with <1 mA base drive; TO-220 tab provides mechanical stability and EMI shielding.

Lamp & LED Dimming

Power Supply Pass Element

Use Scenario: Phase-angle or PWM dimming of incandescent lamps and high-power LED strings in stage lighting systems.

IC Role / Device Role / Timing Role: Series pass switch in low-frequency AC or DC dimming topology.

Use Value: 100 V V_CEO withstands 120 V RMS line peaks; 65 W P_TOT supports 100+ W lamp loads with modest heatsinking.

Use Scenario: Linear regulator pass element in lab-grade bench power supplies delivering up to 5 A output.

IC Role / Device Role / Timing Role: Adjustable series pass transistor controlled by error amplifier feedback loop.

Use Value: Low V_CE(sat) extends dropout margin; high h_FE simplifies current-limit circuit design; R_thJC = 1.92 °C/W enables precise thermal management.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD122G	Surface-mount DPAK package; lower P_TOT (35 W); identical V_CEO/I_C/h_FE specs.	Requires PCB-level thermal vias instead of mechanical heatsink; unsuitable for through-hole legacy designs.	Select when space-constrained PCB layout or automated assembly is prioritized over field-serviceable heatsinking.
TIP127	Complementary PNP Darlington; same package, voltage/current ratings, but inverted polarity.	Used in high-side switch configurations where emitter must connect to positive rail (e.g., floating load topologies).	Choose only for complementary pair design; not a functional substitute in NPN-based circuits.

Compared with MJD122G, TIP122 offers higher power handling and mechanical heatsink compatibility; compared with TIP127, it provides NPN polarity essential for grounded-load switching-making it irreplaceable in standard low-side driver topologies.

Availability

TIP122 is available at Aetrix Electronics and suitable for DC motor control, relay driving, lamp dimming, and linear power supply applications requiring stable component supply, long-term manufacturability, and consistent parametric performance across production batches.

Supply support for TIP122 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, Switzerland, specializing in power management, analog, microcontrollers, and automotive ICs.

The TIP122 belongs to ST's STPOWER bipolar transistor family, engineered for rugged, high-gain power switching in industrial, appliance, and infrastructure equipment where reliability and thermal robustness are critical.

FAQ

Is the metal tab of the TIP122 electrically connected to any pin?

Yes-the metal tab is internally connected to Pin 2 (collector) and forms part of the collector terminal. This requires electrical isolation from the heatsink unless the collector is referenced to chassis ground. Use insulating shoulder washers or mica pads when mounting to conductive heatsinks.

Can the TIP122 be driven directly from a 3.3 V microcontroller GPIO?

Yes-its integrated 7 kΩ base resistor enables reliable turn-on with 3.3 V logic. At 3.3 V, base current is ~0.47 mA, sufficient to saturate the Darlington at ≤1 A load. For 5 A loads, ensure GPIO can source ≥12 mA or add a small buffer stage.

What is the maximum safe continuous current for TIP122 without a heatsink?

Without heatsinking, the device is limited by R_thJA = 62.5 °C/W. At 25°C ambient and 150°C max junction temperature, allowable power is 2 A. Derating to 1.5 A ensures safety margin; forced air or minimal copper pour is recommended above 1 A.

How does the TIP122 differ from the TIP120 and TIP121 in practical use?

TIP122 has higher V_CEO (100 V vs. 60 V for TIP120, 80 V for TIP121), making it mandatory for 100 V bus applications or 120 VAC line-switching. All share identical package, gain, saturation voltage, and thermal specs-only voltage rating differs.

TIP122 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 5 A

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

Vce Saturation (Max) @ Ib, Ic:: 4V @ 20mA, 5A

Current - Collector Cutoff (Max):: 500µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 1000 @ 3A, 3V

Power - Max:: 2 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

TIP122 FAQ

1.How can I place an order for TIP122 through Aetrix?

Please submit a Request for Quotation (RFQ) for TIP122 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 TIP122 reliable?

The price and inventory of TIP122 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TIP122 is usually 5 days.

3.What payment methods are accepted for TIP122?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TIP122 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TIP122?

TIP122 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TIP122 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 TIP122?

For technical support, including TIP122 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TIP122 requirements.

6.How does Aetrix verify that TIP122 is sourced from the original manufacturer or authorized distributors?

All TIP122 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 TIP122 meets industry standards.

7.What is the process for return or replacement of TIP122?

All TIP122 units undergo pre-shipment inspection (PSI). If there is an issue with TIP122, 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 TIP122 part is unused and in its original packaging.

Return procedure for TIP122:

1.Submit a request within 90 days.

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

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