onsemi TIP126G

Overview

TIP126G from onsemi is a PNP silicon Darlington transistor in TO-220AB package, designed for medium-power linear amplification and low-speed switching. It delivers 5.0 A continuous collector current, sustains 80 Vdc collector-emitter voltage (VCEO(sus)), exhibits typical DC current gain (hFE) of 2500 at IC = 4.0 A, and features built-in base-emitter shunt resistors for simplified biasing - commonly used in motor control drivers and relay interface circuits.

For engineers reviewing the TIP126G datasheet, pinout, applications, or equivalent options, key selection criteria include VCEO(sus) rating, saturation voltage under load, thermal resistance (RJC = 1.92 °C/W), safe operating area (SOA) limits, and compatibility with standard TO-220 heatsinking footprints.

Technical Context

The TIP126G integrates two PNP transistors monolithically in Darlington configuration, enabling high current gain with single-base drive. Its internal structure includes integrated base-emitter shunt resistors (~8.0 kΩ and ~120 Ω) to ensure reliable turn-off and reduce external component count.

It operates within –65 °C to +150 °C junction temperature range, supports unclamped inductive load energy up to 50 mJ, and is rated for 65 W total power dissipation at TC = 25 °C - derating linearly at 0.52 W/°C above that temperature.

Key Specifications

Pinout & Package

TO-220AB package with 4-terminal configuration (Style 1): Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter, Pin 4 = Collector (dual-collector design for enhanced current handling and thermal distribution).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP Darlington transistor applications.

Compared with TIP126G, MJD127G trades thermal performance and current capacity for compactness, while TIP127G extends voltage capability without altering mechanical or electrical interface - making it a drop-in replacement where higher VCEO is mandated.

Availability

TIP126G is available at Aetrix Electronics and suitable for industrial motor control, relay interface, linear regulator, heater switching, and DC power supply applications requiring stable component supply and long-term manufacturability.

Supply support for TIP126G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, medical, and IoT markets.

The TIP126G belongs to onsemi's legacy plastic medium-power complementary transistor family, engineered for robust, cost-effective amplification and switching in non-high-frequency industrial and appliance applications.

FAQ

What is the maximum continuous collector current for the TIP126G?

The TIP126G supports 5.0 A continuous collector current (IC) at case temperature TC = 25 °C. This rating assumes proper heatsinking; derating applies above 25 °C at 0.52 W/°C. At higher temperatures or without heatsink, the usable current drops significantly due to thermal limits - always verify junction temperature using RJC = 1.92 °C/W and actual power dissipation in your layout. The TIP126G must not exceed its SOA curve under pulsed conditions.

Does the TIP126G have built-in base resistors?

Yes, the TIP126G incorporates monolithic base-emitter shunt resistors (~8.0 kΩ and ~120 Ω) as part of its Darlington structure. These resistors ensure reliable turn-off by discharging stored base charge, reducing external component count, and preventing false triggering from leakage currents. This feature distinguishes the TIP126G from standard PNP transistors and simplifies drive circuit design - no external pull-down resistor is required for basic switching operation.

What is the collector-emitter sustaining voltage (VCEO(sus)) of the TIP126G?

The TIP126G has a minimum collector-emitter sustaining voltage VCEO(sus) of 80 Vdc at IC = 100 mAdc and IB = 0. This parameter reflects the device's ability to block voltage in the off state under transient overvoltage conditions - distinct from static VCEO. It is validated per note 2 in the datasheet using pulse testing (300 µs width, 2% duty cycle). For sustained DC blocking, refer to the absolute maximum VCEO rating of 80 Vdc.

Can the TIP126G be used in linear regulator applications?

Yes, the TIP126G is routinely used as a series pass element in linear voltage regulators due to its high hFE (2500 typ), low VCE(sat), and 65 W power dissipation capability with heatsinking. Its Darlington configuration reduces base drive requirements, and built-in shunt resistors improve stability. However, thermal design is critical: ensure junction temperature stays below 150 °C using RJC = 1.92 °C/W and appropriate heatsink thermal resistance. The TIP126G is not recommended for high-frequency switching (>10 kHz) due to limited bandwidth.

Is the TIP126G pin-compatible with other TIP12x devices?

Yes, the TIP126G shares identical TO-220AB (Case 221A) packaging and Style 1 pinout (Pin 1 = Base, Pins 2 & 4 = Collector, Pin 3 = Emitter) with all TIP120–TIP127 variants, including TIP125G and TIP127G. This allows direct physical replacement on PCBs. However, electrical differences exist: TIP125G has VCEO(sus) = 60 Vdc, while TIP127G offers 100 Vdc - always verify voltage and SOA requirements before substitution. The TIP126G itself is not pin-compatible with NPN types like TIP120G due to polarity reversal.