onsemi 2N5550BU

Overview

2N5550BU from ON Semiconductor is an NPN epitaxial silicon transistor designed for general-purpose amplifier and switching applications, featuring V_CEO = 140 V, I_C = 600 mA, h_FE = 60–250 (at I_C = 1–10 mA), f_T = 100–300 MHz, and TO-92 3L package. It operates reliably in audio preamplifier stages, relay drivers, and low-power linear regulators.

For engineers reviewing the 2N5550BU datasheet, pinout, applications, or equivalent options, key selection criteria include breakdown voltage margin, DC current gain linearity at 1–50 mA, saturation voltage under defined base drive, thermal resistance (R_θJA = 200 °C/W), and noise figure (NF = 10 dB) in low-level signal amplification.

Technical Context

This discrete NPN bipolar junction transistor uses epitaxial base construction to achieve high f_T and stable h_FE across collector currents from 1 mA to 50 mA. Its V_CEO = 140 V and V_CBO = 160 V support medium-voltage analog and switching circuits where robust off-state blocking is required.

The device exhibits V_CE(sat) = 0.15 V at I_C = 10 mA / I_B = 1 mA and V_BE(sat) = 1.0 V under same conditions, enabling efficient low-loss switching in discrete driver stages. Cob = 6 pF at V_CB = 10 V ensures minimal Miller effect in RF-coupled amplifier designs up to 100 MHz.

Key Specifications

Pinout & Package

2N5550BU is housed in a JEDEC TO-92 3L molded plastic package with straight leads (bulk packing). The case outline conforms to standard TO-92 mechanical dimensions, with lead spacing of 0.2 inch and body height ≤ 4.7 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose amplifier applications.

Compared with 2N5551BU and MPSA42, the 2N5550BU delivers optimal balance of gain linearity, noise, and voltage rating for sub-150 V amplifier and switching tasks-making it preferred for cost-sensitive consumer and industrial signal conditioning where 140 V suffices.

Availability

2N5550BU is available at Aetrix Electronics and suitable for audio preamplifiers, relay drivers, and linear voltage regulator pass elements requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for 2N5550BU 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 supplier delivering energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, medical, and IoT applications.

The 2N5550BU belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, originally developed by Fairchild Semiconductor for reliable, low-cost amplification and switching in non-critical analog and digital interface circuits.

FAQ

What is the maximum collector-emitter voltage rating for the 2N5550BU?

The 2N5550BU has a guaranteed minimum collector-emitter breakdown voltage (BV_CEO) of 140 V at I_C = 1 mA and I_B = 0. This rating is validated per JEDEC test conditions and defines the absolute upper limit for safe DC or pulsed operation without avalanche conduction. Exceeding 140 V risks irreversible device failure. The 2N5550BU must be operated within this limit in all circuit configurations, including inductive load switching with flyback spikes.

Does the 2N5550BU have a specified noise figure, and under what conditions is it measured?

Yes, the 2N5550BU has a specified noise figure of 10 dB, measured at I_C = 250 μA, V_CE = 5 V, R_S = 1 kΩ, and frequency range 10 Hz to 15.7 kHz. This value reflects its suitability for low-level analog signal amplification, such as electret microphone preamplifiers or sensor front-ends. The 2N5550BU's noise performance is not characterized outside this specific test setup, and actual noise in customer designs depends on PCB layout, biasing, and source impedance matching.

What is the thermal resistance junction-to-ambient (R_θJA) for the 2N5550BU, and how does it affect power dissipation?

The 2N5550BU has an R_θJA of 200 °C/W under standard FR-4 PCB conditions (76 mm × 114 mm, 1.57 mm thick, minimum copper land pattern). This means each watt of power dissipated raises the junction temperature by 200 °C above ambient. Since the 2N5550BU's maximum junction temperature is 150 °C, its usable power dissipation drops from 625 mW at 25 °C ambient to zero at 150 °C ambient-requiring derating at 5.0 mW/°C above 25 °C. Proper board layout is essential to maintain this R_θJA value for the 2N5550BU.

Is the 2N5550BU pin-compatible with other TO-92 NPN transistors like the 2N2222A?

No-the 2N5550BU uses the standard TO-92 pinout (1 = Emitter, 2 = Base, 3 = Collector), which matches the 2N2222A and most JEDEC-compliant TO-92 NPN transistors. However, electrical parameters differ significantly: the 2N5550BU offers higher V_CEO (140 V vs. 40 V) and higher f_T (100–300 MHz vs. ~250 MHz), but lower h_FE minimum at low current. Substituting the 2N5550BU for a 2N2222A requires verifying bias stability and voltage margins in the target circuit, as the 2N5550BU is not a drop-in replacement despite identical pinout.

What packaging options are available for the 2N5550BU, and how do they differ from other 2N5550 variants?

The 2N5550BU is supplied in bulk packaging, distinguishing it from tape-and-reel (2N5550TF, 2N5550TFR) and ammo pack (2N5550TA, 2N5550TAR) variants-all sharing identical TO-92 3L package and electrical specifications. Bulk format suits manual assembly, prototyping, and low-volume production, while tape-and-reel supports automated pick-and-place. The "BU" suffix explicitly denotes bulk; no functional or parametric differences exist between 2N5550BU and other 2N5550 variants beyond packing method.