onsemi TIP31A

Overview

TIP31A from onsemi is an NPN silicon power transistor in TO-220AB package, rated for 60 V_CEO, 3.0 A continuous collector current, and 40 W total power dissipation at T_C = 25°C. It delivers V_CE(sat) ≤ 1.2 V at I_C = 3.0 A and exhibits f_T ≥ 3.0 MHz, making it suitable for medium-power linear amplification and switching in DC motor drivers and power supply regulators.

For engineers reviewing the TIP31A datasheet, pinout, applications, or equivalent options, key selection criteria include its 60 V V_CEO rating, TO-220AB thermal performance (R_θJC = 3.125°C/W), saturation voltage under high-current drive, safe operating area (SOA) limits, and complementary PNP pairing with TIP32A.

Technical Context

The TIP31A operates as a general-purpose NPN bipolar junction transistor optimized for linear and switching modes. Its DC current gain (h_FE) ranges from 10 to 50 depending on I_C, and it supports fast switching with turn-on time ≤7.0 ns and turn-off time <15 ns under specified test conditions.

Thermal design relies on its low junction-to-case thermal resistance (3.125°C/W) and defined derating curve-power dissipation drops linearly above 25°C ambient or case temperature. The device's SOA is limited by both thermal constraints and secondary breakdown, with pulse operation validated up to 5 ms at 150°C peak junction temperature.

Key Specifications

Pinout & Package

Package: TO-220AB (Case 221A-09), 4-lead plastic power package with two collector terminals (pins 2 and 4), one base (pin 1), and one emitter (pin 3). Mounting tab is electrically connected to collector.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD31C and BD139, the TIP31A provides superior thermal performance (3.125°C/W vs. ≥4°C/W), higher continuous current (3.0 A vs. ≤1.5 A), and proven ruggedness for inductive loads-making it the preferred choice for robust through-hole power switching where heatsink integration is critical.

Availability

TIP31A is available at Aetrix Electronics and suitable for DC motor control, linear power supply regulation, audio amplifier output stages, and relay/solenoid driving requiring stable component supply across industrial production cycles.

Supply support for TIP31A 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 focused on energy-efficient electronics, delivering discrete, analog, and power management solutions.

The TIP31A belongs to onsemi's legacy silicon power transistor family designed for cost-sensitive, medium-power linear and switching applications in industrial, consumer, and automotive auxiliary systems.

FAQ

What is the maximum collector-emitter voltage rating for the TIP31A?

The TIP31A has a minimum collector-emitter sustaining voltage (V_CEO(sus)) of 60 Vdc under specified test conditions (I_C = 30 mA, I_B = 0). This rating ensures reliable operation in circuits where transient voltages do not exceed this threshold, such as 48 V nominal power rails or 24 V motor drives with inductive kickback suppression. Exceeding 60 V risks avalanche breakdown unless external clamping is applied.

Can the TIP31A be used as a direct replacement for the TIP31 in existing designs?

No-the TIP31A is not a drop-in replacement for the TIP31 due to differing voltage ratings: TIP31A specifies V_CEO ≥ 60 V, while TIP31 is rated only ≥ 40 V. Substituting TIP31A into a TIP31-design may be safe if the circuit never exceeds 40 V, but the higher rating does not guarantee identical SOA, gain, or thermal behavior. Always verify safe operating area, base drive requirements, and thermal margin when swapping variants.

What is the recommended base resistor value to fully saturate the TIP31A at 3.0 A collector current?

To achieve saturation at I_C = 3.0 A, the TIP31A requires I_B ≥ 375 mA per datasheet test condition (V_CE(sat) measured at I_B = 375 mA). With a typical V_BE(on) of 1.8 V and 5 V logic drive, a 8.5 Ω resistor yields ~376 mA base current. For reliability, use 8.2 Ω ±5% 2 W resistor to handle peak power and maintain saturation across temperature and unit variation.

Does the TIP31A have integrated ESD or overvoltage protection?

No-the TIP31A is a bare silicon bipolar transistor with no integrated protection features. It lacks ESD diodes, built-in base-emitter clamp, or collector-emitter transient suppressors. External components-including base-emitter reverse-bias protection diodes, collector flyback diodes for inductive loads, and input series resistors-are mandatory for robust operation in real-world environments.

How does the dual-collector pin configuration (pins 2 and 4) affect PCB layout for the TIP31A?

The dual-collector pins (2 and 4) in the TO-220AB package of the TIP31A are internally shorted and connected to the metal mounting tab. This design improves current handling and thermal conduction-both pins must be routed to the same net (typically ground or supply rail) and soldered to a large copper pour or heatsink. Splitting these pins or routing them separately violates the internal construction and risks overheating or bond-wire failure.