onsemi MJE371G

Overview

MJE371G from onsemi is a plastic medium-power PNP silicon transistor designed for general-purpose amplifier and switching circuits, with 40 V_CEO, 4.0 A_C continuous collector current, 40 W total power dissipation at T_C = 25°C, and complementary pairing to NPN MJE521 - recommended for 5–20 W audio amplifiers using complementary symmetry topology.

For engineers reviewing the MJE371G datasheet, pinout, applications, or equivalent options, key selection considerations include safe operating area (SOA) limits at T_J(pk) = 150°C, thermal resistance R_JC = 3.12°C/W, DC current gain h_FE ≥ 40 at I_C = 1.0 A/V_CE = 1.0 V, V_EB = 4.0 Vdc maximum, and TO-225 package mechanical compatibility.

Technical Context

The MJE371G operates as a bipolar junction transistor in linear amplification and saturated switching modes, with specified SOA boundaries governed by thermal limit (T_J ≤ 150°C) and second breakdown constraints. Its h_FE performance is characterized across –55°C to +150°C, showing normalized gain degradation at elevated temperature.

It features fixed terminal assignment per TO-225 Style 1: Emitter at Pin 1, Collector at Pins 2 & 4 (internally tied), Base at Pin 3. Saturation parameters include V_BE(sat) and V_CE(sat) measured at I_C/I_B = 10, supporting reliable bias design in Class AB audio output stages.

Key Specifications

Pinout & Package

Package: TO-225 (Case 77-09, Style 1), plastic medium-power outline with metal tab (Pins 2 & 4 internally connected to collector, tab electrically tied to collector).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power transistor applications.

Compared with MJE371G, MJE372G offers higher voltage headroom without sacrificing current or thermal capability, while BD140 trades power handling for compactness and voltage margin - neither is pin-compatible, requiring PCB layout revision.

Availability

MJE371G is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, linear voltage regulators, and relay interface circuits requiring stable component supply and industrial-grade reliability.

Supply support for MJE371G 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MJE371G belongs to onsemi's legacy discrete power transistor family, engineered specifically for cost-sensitive, medium-power analog and switching applications demanding proven reliability and thermal stability in TO-225 packaging.

FAQ

What is the maximum continuous collector current rating for the MJE371G?

The MJE371G has a maximum continuous collector current (I_C) rating of 4.0 Adc at T_C = 25°C. This rating decreases with rising case temperature, following a derating slope of 320 mW/°C for power dissipation. At T_C = 100°C, the usable I_C drops to approximately 2.4 A based on SOA constraints and thermal limits. Always verify actual operating I_C against the SOA curve in Figure 1 of the MJE371G datasheet.

Is the MJE371G pin-compatible with the MJE521 NPN transistor?

No, the MJE371G is not pin-compatible with the MJE521. While they are complementary devices (PNP vs. NPN) intended for symmetric circuit design, their pinouts differ: MJE371G uses TO-225 Style 1 (Emitter–Collector–Base–Collector), whereas MJE521 uses TO-225 Style 3 (Base–Collector–Emitter). Physical layout must account for reversed terminal order when implementing push-pull pairs - the MJE371G cannot be substituted for MJE521 without board modification.

Does the MJE371G support operation at elevated temperatures?

Yes, the MJE371G is rated for junction and storage temperatures from –65°C to +150°C. Its h_FE and V_CE(sat) characteristics are characterized across this range, with Figure 2 showing normalized gain retention down to –55°C and up to +150°C. However, power dissipation must be strictly limited per the derating curve and SOA diagram to prevent thermal runaway at high ambient temperatures.

What does the "G" suffix signify in MJE371G?

The "G" suffix in MJE371G indicates a Pb-free (lead-free) package compliant with the EU RoHS Directive 2011/65/EU. It confirms that all solderable terminations and internal construction meet RoHS material restrictions, including absence of lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE. The "G" does not denote a functional variant - electrical and thermal specifications are identical to non-G versions unless otherwise stated in the datasheet.

Can the MJE371G be used in switching applications with fast PWM signals?

The MJE371G is optimized for medium-speed switching (e.g., audio-frequency and DC motor control), not high-frequency PWM. Its transition frequency f_T is not specified in the datasheet, and its stored charge and fall time are not characterized for >10 kHz operation. For PWM-driven loads above 20 kHz, consider RF-optimized or MOSFET alternatives. In 1–10 kHz motor or relay switching, the MJE371G performs reliably when base drive is sized to ensure saturation and avoid quasi-saturation delay.