onsemi MJE5851

Overview

MJE5851 from onsemi is a PNP silicon power transistor designed for high-voltage, high-speed switching in inductive circuits where fast fall time is critical-specifically rated for 350 V_CEO(sus), 8 A continuous collector current, and 80 W total power dissipation in TO-220 package. It serves as a line-operated switch-mode power transistor in deflection circuits, motor controls, and solenoid drivers.

For engineers reviewing the MJE5851 datasheet, pinout, applications, or equivalent options, key selection criteria include its 350 V sustained collector-emitter voltage, 0.11–0.5 μs fall time under resistive load, 100°C-rated RBSOA with inductive clamping, TO-220 mechanical outline (Case 221A-09), and complementary pairing with MJE13007 series devices.

Technical Context

The MJE5851 operates as a high-voltage PNP bipolar junction transistor optimized for inductive switching, with guaranteed performance at 100°C junction temperature-including clamped inductive SOA, storage time (t_sv), and crossover time (t_c). Its base-emitter reverse bias capability up to 6 V enables robust turn-off control in flyback and snubber-assisted topologies.

It features a thermal resistance of 1.25°C/W (junction-to-case), supports peak collector current up to 16 A, and delivers DC current gain (h_FE) ≥15 at I_C = 2.0 A and V_CE = 5 V. Saturation voltage is specified at 2.0–2.5 V across operating temperatures, ensuring predictable conduction loss in hard-switched applications.

Key Specifications

Pinout & Package

Package: TO-220 (Case 221A-09), 3-pin variant (Style 1), with pins 2 and 4 both connected to collector. Mounting tab is electrically connected to collector.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP high-voltage switching transistor applications.

Compared with MJE5851, the MJE5852 offers higher voltage headroom but increased cost and slightly higher leakage, while the MJE13009 provides higher current capability in NPN configuration-neither is pin-compatible, but both serve adjacent roles in high-voltage switching system design.

Availability

MJE5851 is available at Aetrix Electronics and suitable for horizontal deflection circuits, solenoid drivers, brushed DC motor controls, and offline flyback power supplies requiring stable component supply and long-term industrial availability.

Supply support for MJE5851 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 power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and IoT applications.

The MJE5851 belongs to onsemi's Switch-mode Series of PNP silicon power transistors-designed specifically for high-voltage, high-speed inductive switching where fall time and RBSOA performance at elevated temperature are critical.

FAQ

What is the maximum collector-emitter sustaining voltage for the MJE5851?

The MJE5851 has a maximum collector-emitter sustaining voltage (V_CEO(sus)) of 350 Vdc, tested with I_C = 10 mA and I_B = 0. This rating applies under switching conditions with inductive loads and defines the highest voltage the device can block reliably before breakdown. The MJE5851 datasheet confirms this value is guaranteed across the full operating temperature range and forms the basis for safe operating area (SOA) calculations in line-operated designs.

Does the MJE5851 support operation at elevated junction temperatures?

Yes, the MJE5851 is fully characterized and guaranteed at 100°C junction temperature for key parameters including reversed biased SOA, switching times with inductive loads, saturation voltages, and leakage currents. Its −65°C to +150°C operating range and 100°C performance specifications make it suitable for thermally demanding environments such as enclosed motor drives and industrial power supplies where ambient temperatures exceed 70°C.

What is the pin configuration of the MJE5851 in its TO-220 package?

The MJE5851 uses TO-220 Case 221A-09 Style 1 pinout: Pin 1 is Base, Pin 2 is Collector, Pin 3 is Emitter, and Pin 4 is Collector (electrically tied to Pin 2). The metal tab is internally connected to the collector, requiring electrical isolation when mounted to heatsinks. This dual-collector configuration improves current sharing and thermal conduction in high-power switching applications.

How does the MJE5851 compare to the MJE5850 and MJE5852 in terms of voltage rating?

The MJE5851 sits between the MJE5850 (300 V_CEO(sus)) and MJE5852 (400 V_CEO(sus)) in the same family-offering 350 V_CEO(sus) with identical package, thermal characteristics, and switching performance. All three share the same TO-220 footprint and pinout, allowing layout reuse across voltage grades, though each must be selected based on actual bus voltage and safety margin requirements in the final design.

Is the MJE5851 suitable for use in switch-mode power supplies?

Yes, the MJE5851 is explicitly designed for line-operated switch-mode applications, including flyback and forward converters. Its fast fall time (0.11–0.5 μs), low crossover time (≤1.5 μs), and 100°C-rated RBSOA enable efficient high-frequency switching with minimal loss during turn-off transitions. The MJE5851 datasheet cites switching regulators and deflection circuits as primary use cases, confirming its suitability for SMPS primary-side switching up to 100 kHz.