onsemi MJD31CTF

Overview

MJD31CTF from ON Semiconductor is an NPN epitaxial silicon power transistor in TO-252 (DPAK) package, rated for 100 V V_CEO, 3 A continuous collector current, and 15 W collector dissipation at T_C = 25°C. It serves as a general-purpose amplifier or low-speed switch in DC-DC converter output stages and linear power amplifier driver circuits.

For engineers reviewing the MJD31CTF datasheet, pinout, applications, or equivalent options, key selection criteria include its 100 V breakdown rating, 3 A DC current capability, 1.2 V V_CE(sat) at I_C = 3 A / I_B = 375 mA, h_FE range of 10–50 at I_C = 3 A, and surface-mount DPAK thermal performance.

Technical Context

This device operates as a medium-power bipolar junction transistor with fixed NPN polarity and non-isolated emitter-collector-base topology. Its design targets linear amplification and switching below 3 MHz (f_T = 3 MHz), with V_BE(on) = 1.8 V at I_C = 3 A and safe operating area validated up to 100 V / 3 A DC conditions.

Thermal derating begins at T_C > 25°C, reducing maximum power dissipation linearly to zero at 150°C case temperature. Electrical isolation between collector and mounting tab is not provided - the collector connects internally to the DPAK heatsink pad.

Key Specifications

Pinout & Package

Package: TO-252-3 (DPAK), surface-mount, single heatsink tab (collector-connected). Dimensions per JEDEC TO-252 VAR. AB standard; 6.7 mm × 6.2 mm body, 0.95 mm nominal thickness, 2.3 mm lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD31CTF, the MJD31C offers identical electrical behavior but different packaging logistics, while the BD139 requires layout changes and sacrifices 20 V headroom and 2.5 W thermal capacity - making MJD31CTF preferable for new 48 V or higher-power SMT designs.

Availability

MJD31CTF is available at Aetrix Electronics and suitable for switching regulators, DC-DC converters, and linear power amplifiers requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for MJD31CTF 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

ON Semiconductor is a global semiconductor manufacturer specializing in power management, analog, sensor, and logic devices for automotive, industrial, cloud power, and IoT applications.

The MJD31CTF belongs to ON Semiconductor's general-purpose power transistor product line, designed for cost-sensitive, medium-power linear and switching applications where robustness, thermal reliability, and surface-mount compatibility are essential.

FAQ

What is the maximum continuous collector current rating for the MJD31CTF?

The MJD31CTF has a maximum continuous collector current (I_C) rating of 3 A at T_C = 25°C. This rating assumes adequate heatsinking; current must be derated linearly as case temperature rises above 25°C, reaching zero at 150°C. At 100°C case temperature, the usable I_C drops to approximately 1.5 A. The MJD31CTF datasheet specifies this limit under DC conditions - pulse current up to 5 A is allowed for short durations (≤300 μs, duty cycle ≤2%).

Is the MJD31CTF pin-compatible with the TIP31C?

No, the MJD31CTF is not pin-compatible with the TIP31C. While electrically similar per the datasheet, the MJD31CTF uses a TO-252 (DPAK) surface-mount package with pins arranged Base–Collector–Emitter, whereas the TIP31C uses a TO-220 through-hole package with Collector–Base–Emitter pinout and a metal tab connected to the collector. Physical layout, mounting method, and thermal interface differ significantly - direct substitution requires PCB redesign.

What is the typical V_CE(sat) of the MJD31CTF under full-load conditions?

The typical V_CE(sat) of the MJD31CTF is 1.2 V when operated at I_C = 3 A and I_B = 375 mA, measured at T_A = 25°C. This value represents the voltage drop across the collector-emitter junction in saturation and directly determines conduction loss (P_cond ≈ 3.6 W at full load). The MJD31CTF datasheet lists this as a maximum specification; actual units typically measure between 1.0 V and 1.2 V under those exact conditions.

Does the MJD31CTF have built-in ESD protection?

No, the MJD31CTF does not include integrated ESD protection circuitry. As a discrete bipolar power transistor, it relies on external handling precautions (e.g., grounded workstations, anti-static packaging) and board-level protection (e.g., series resistors, TVS diodes) during assembly and operation. The MJD31CTF datasheet specifies no human-body-model (HBM) or charged-device-model (CDM) ESD ratings - users must implement system-level safeguards per IEC 61000-4-2 requirements.

Can the MJD31CTF be used in linear regulator pass transistor applications?

Yes, the MJD31CTF can be used as a pass transistor in linear voltage regulators, provided thermal design accounts for worst-case power dissipation. For example, regulating 48 V down to 12 V at 2 A yields 72 W of power dissipation - far exceeding the MJD31CTF's 15 W rating. Practical use requires input-output differentials ≤5 V at 3 A (≤15 W), such as 12 V → 5 V conversion. The MJD31CTF's h_FE stability and SOA compliance support this role when heatsinked appropriately and current-limited externally.