onsemi MPSL51

Overview

MPSL51 from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor designed for high-voltage amplification and switching applications, with V_CEO = 100 V, I_C = 200 mA, h_FE = 40–250 at 50 mA, f_T = 60 MHz, and TO-92 package. It serves in discrete signal conditioning and power control stages of industrial timers, relay drivers, and low-frequency analog amplifiers.

For engineers reviewing the MPSL51 datasheet, pinout, applications, or equivalent options, key selection criteria include its PNP polarity, 100 V breakdown rating, saturation voltage under defined drive conditions, thermal resistance (R_θJA = 200 °C/W), and compatibility with legacy 2N5401-based designs requiring similar DC gain and switching speed.

Technical Context

The MPSL51 operates as a silicon PNP BJT fabricated using Fairchild's Process 74, optimized for stable DC current gain and reliable high-voltage operation up to 100 V across collector-emitter and collector-base terminals. Its f_T of 60 MHz supports audio-frequency amplification and moderate-speed switching.

Thermal design relies on its R_θJA of 200 °C/W and R_θJC of 83.3 °C/W, with maximum junction temperature rated at +150 °C. The device exhibits V_CE(sat) ≤ 0.3 V at I_C = 50 mA / I_B = 5 mA and V_BE(sat) = 1.2 V under same conditions - critical for low-loss switching in emitter-follower or common-emitter configurations.

Key Specifications

Pinout & Package

Package: TO-92 - standard 3-lead through-hole plastic package with lead spacing of 0.500", flat side orientation per Fairchild Figure 1.0, and mechanical dimensions compliant with JEDEC TO-92 outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP amplifier and switching applications.

Compared with 2N5401 and MPSA92, the MPSL51 delivers identical high-voltage PNP functionality in TO-92 with verified 60 MHz f_T and tighter thermal resistance specification (R_θJA = 200 °C/W), making it preferable for thermally constrained PCB layouts where gain stability at elevated ambient temperatures is critical.

Availability

MPSL51 is available at Aetrix Electronics and suitable for industrial relay drivers, audio pre-amplifier stages, high-voltage level shifters, and discrete power supply error amplifiers requiring stable component supply and long-lifecycle support.

Supply support for MPSL51 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The MPSL51 belongs to Fairchild's general-purpose PNP transistor family, engineered for reliability in high-voltage switching and linear amplification roles across industrial control, instrumentation, and legacy analog systems.

FAQ

What is the maximum collector-emitter voltage rating for the MPSL51?

The MPSL51 has a maximum collector-emitter voltage (V_CEO) rating of 100 V at T_A = 25 °C. This rating is confirmed in both Absolute Maximum Ratings and OFF CHARACTERISTICS sections of the official Fairchild datasheet. Exceeding this voltage risks permanent breakdown. Derating is recommended above 25 °C ambient per the specified thermal characteristics. The MPSL51 maintains this 100 V rating consistently across its full operating temperature range.

Is the MPSL51 pin-compatible with the 2N5401?

Yes, the MPSL51 is pin-compatible with the 2N5401 - both use the TO-92 package with identical lead assignments (Emitter, Base, Collector in same physical order). The datasheet explicitly references "See 2N5401 for characteristics", confirming functional and mechanical alignment. No PCB layout changes are required when substituting MPSL51 for 2N5401 in existing designs, provided thermal and gain requirements remain within spec.

What is the typical DC current gain (h_FE) of the MPSL51 at 50 mA collector current?

The MPSL51 exhibits a DC current gain (h_FE) ranging from 40 to 250 when tested at V_CE = 5.0 V and I_C = 50 mA. This wide range reflects standard BJT process variation and must be accounted for in bias design. For robust operation, circuits should function correctly across the full 40–250 span. The MPSL51's h_FE performance is consistent with its role as a general-purpose amplifier and aligns with legacy equivalents like the 2N5401.

Does the MPSL51 support switching applications, and what is its saturation voltage?

Yes, the MPSL51 supports switching applications with V_CE(sat) ≤ 0.25 V at I_C = 10 mA / I_B = 1.0 mA and ≤ 0.3 V at I_C = 50 mA / I_B = 5.0 mA. These values confirm low conduction loss in saturated mode. The MPSL51's switching behavior is validated by its f_T of 60 MHz and fast recovery characteristics implied by Cob = 8.0 pF. Designers can rely on the MPSL51 for efficient on/off control in relay drivers and power logic interfaces.

What is the thermal resistance from junction to ambient (R_θJA) for the MPSL51 in TO-92 package?

The MPSL51 has a junction-to-ambient thermal resistance (R_θJA) of 200 °C/W when mounted on a standard FR-4 PCB with no added heatsink. This value is specified in the Thermal Characteristics table and assumes natural convection cooling. At 25 °C ambient, the device reaches its 150 °C maximum junction temperature at approximately 313 mW dissipation - below its 625 mW rated P_D. The MPSL51's R_θJA is critical for thermal margin analysis in compact industrial enclosures.