onsemi MJE182

Overview

MJE182 from STMicroelectronics is an NPN low-voltage, high-speed switching transistor in SOT-32 (TO-126) package, rated for V_CEO = 80 V, I_C = 3 A, and f_T = 50 MHz, designed for audio amplification and low-current switching circuits in consumer and industrial electronics.

For engineers reviewing the MJE182 datasheet, MJE182 pinout, MJE182 application, or MJE182 equivalent, key selection criteria include saturation voltage at 3 A (V_CE(sat) ≤ 1.7 V), DC current gain (h_FE = 12–250), thermal resistance (R_thJC = 10 °C/W), and SOT-32 mechanical compatibility with TO-126 footprint layouts.

Technical Context

The MJE182 uses epitaxial planar technology to achieve fast switching response and stable gain across collector currents from 0.1 A to 3 A. Its V_BE(sat) of 1.5–2.0 V at high drive ensures reliable turn-on with standard TTL/CMOS logic-level base drive.

Designed for operation up to T_J = 150 °C, it features low R_thJC (10 °C/W) and moderate R_th-amb (83.3 °C/W), enabling direct heatsink mounting via the collector tab while maintaining safe junction temperature under 12.5 W continuous dissipation at T_C ≤ 25 °C.

Key Specifications

Pinout & Package

The MJE182 is housed in a SOT-32 (TO-126) plastic package with a metal tab connected to the collector for thermal and electrical grounding. The case serves as the collector terminal, and the device is mounted using the tab for heatsinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC337-40 and TIP31A, the MJE182 uniquely balances 3 A current handling, 80 V voltage rating, and 50 MHz bandwidth-making it optimal for mid-power audio and high-frequency switching where both thermal robustness and dynamic response matter.

Availability

MJE182 is available at Aetrix Electronics and suitable for audio amplifier output stages, relay driver circuits, DC motor control modules, and LED array power switching requiring stable component supply and long-term BOM continuity.

Supply support for MJE182 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 discrete devices for industrial, automotive, and consumer markets.

The MJE182 belongs to ST's legacy bipolar transistor product line, engineered specifically for cost-sensitive, medium-power linear and switching applications where reliability, thermal performance, and TO-126 compatibility are essential.

FAQ

Is the MJE182 still in active production?

No-the MJE182 is marked "Obsolete Product(s)" in ST's official documentation (Doc ID 022074 Rev 1, August 2011). While not actively manufactured, Aetrix Electronics maintains legacy inventory and offers traceable, tested stock for continuity-critical designs and repair programs.

Can the MJE182 replace a TIP31C in an existing design?

Yes, with verification: both use SOT-32 (TO-126) packages and share pinout (C-B-E), but the MJE182 has higher V_CEO (80 V vs. 100 V for TIP31C) and significantly higher f_T (50 MHz vs. ~3 MHz). Confirm that 80 V margin suffices and that layout supports its faster switching behavior.

What is the maximum safe continuous power dissipation at 70 °C case temperature?

Using R_thJC = 10 °C/W and T_J(max) = 150 °C, the allowable ΔT is 80 °C. Thus, P_D(max) = 80 °C ÷ 10 °C/W = 8 W at T_C = 70 °C. This is derated from the 12.5 W rating at T_C = 25 °C per the datasheet's thermal curve.

Does the MJE182 require a heatsink in typical 1 A switching applications?

At I_C = 1 A and V_CE(sat) ≈ 0.9 V, power dissipation is ~0.9 W. With R_th-amb = 83.3 °C/W, junction rise would be ~75 °C above ambient-acceptable without heatsink if ambient stays ≤ 75 °C. For sustained operation >1 A or in enclosed environments, a small clip-on heatsink is recommended.