Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi 2N5551

Name: 2N5551
Brand: onsemi
SKU: 2N5551
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: 2N5551

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 Long Body

Datasheet:: 2N5551.pdf

Description:: TRANS NPN 160V 0.6A TO92

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:3,006

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

2N5551 from onsemi is an NPN silicon general-purpose amplifier transistor in TO-92 package, rated for 160 V_CEO, 180 V_CBO, 600 mA continuous collector current, and 625 mW power dissipation at 25°C ambient. It delivers DC current gain (h_FE) of 80–250 at I_C = 1.0–50 mA and supports high-frequency amplification up to 300 MHz f_T, commonly used in low-noise preamplifier stages and switching circuits.

For engineers reviewing the 2N5551 datasheet, pinout, applications, or equivalent options, key selection considerations include its 160 V breakdown rating, 8.0 dB noise figure at 250 µA, TO-92 mechanical compatibility, and verified performance across −55°C to +150°C junction temperature range.

Technical Context

The 2N5551 operates as a discrete NPN bipolar junction transistor optimized for medium-voltage linear amplification and fast-switching applications. Its design emphasizes high V_CEO/V_CBO margin, low saturation voltage (V_CE(sat) = 0.25 V at I_C/I_B = 10), and stable h_FE over temperature - with gain variation bounded between 25°C and 125°C per Figure 1.

It exhibits 6.0 pF output capacitance (C_obo) and 20 pF input capacitance (C_ibo) at specified bias conditions, supporting bandwidth-critical designs. The device's 100–300 MHz f_T range and 8.0 dB noise figure at I_C = 250 µA make it suitable for RF front-end and audio preamp roles where signal integrity and gain stability are prioritized.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	160 Vdc - supports operation in 120 V rail systems with 33% safety margin
I_C (continuous)	600 mAdc - enables drive capability for small relays, LED arrays, or logic-level interface loads
P_D @ T_A = 25°C	625 mW - limits thermal derating to 5.0 mW/°C above ambient, requiring heatsinking above ~75°C
h_FE	80–250 - provides predictable DC gain across 1–50 mA collector currents for bias-stable amplifier designs
f_T	100–300 MHz - ensures usable gain in VHF band amplifiers and broadband signal conditioning
NF	8.0 dB @ I_C = 250 µA - meets low-noise requirements for microphone preamps and sensor signal chains
R_JA	200 °C/W - defines thermal path limitation for PCB layout; requires ≥1 cm² copper pour for sustained 500 mW operation

Pinout & Package

Package: TO-92 (Case 29-11), through-hole, Pb-free compliant, 3-pin vertical mounting with E-B-C pin order (Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector).

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Reference node for base-emitter bias; connects to ground or low-impedance return path in common-emitter configurations
2 (Base)	Control input	Accepts current-limited drive (typically ≤5% of I_C) to modulate collector current; sensitive to ESD due to thin oxide layer
3 (Collector)	Current source terminal	Delivers amplified output current; must be isolated from high dV/dt nodes to avoid secondary breakdown in switching use

Key Features

Feature	Design Value
High V_CBO (180 V)	Enables safe operation in inductive load switching with flyback voltage spikes up to 160 V
Low V_CE(sat) (0.25 V)	Reduces conduction loss in saturated switch mode, improving efficiency in 5–12 V logic-driven circuits
Stable h_FE vs. temperature	Maintains consistent DC bias points across industrial temperature range without active compensation
Low noise figure (8.0 dB)	Preserves SNR in analog front-ends handling microvolt-level signals from piezoelectric or electret sources
TO-92 mechanical standardization	Ensures drop-in replacement compatibility with legacy designs using 2N2222, PN2222, or BC547 footprints

Applications

Audio Preamplifier Stage	High-Voltage Switch Driver
Use Scenario: Amplifying weak signals from electret microphones or magnetic pickups before ADC sampling. IC Role / Device Role / Timing Role: Discrete NPN transistor configured in common-emitter topology for voltage gain and impedance transformation. Use Value: 8.0 dB noise figure and 200 MHz f_T preserve wideband fidelity while enabling single-stage gain >100 without oscillation risk.	Use Scenario: Driving relay coils or small solenoids from 5 V or 12 V microcontroller GPIO pins. IC Role / Device Role / Timing Role: Saturated switch controlling inductive load current with minimal power loss. Use Value: 0.25 V V_CE(sat) at 50 mA reduces heat generation by >40% versus older 2N2222 variants, extending reliability in cyclic duty applications.
RF Signal Buffer	Industrial Sensor Interface
Use Scenario: Isolating and buffering 27–100 MHz RF signals in amateur radio receiver front-ends. IC Role / Device Role / Timing Role: Common-collector emitter-follower providing low-output-impedance drive without phase inversion. Use Value: 20 pF C_ibo and 300 MHz f_T support stable unity-gain operation with <1 dB insertion loss up to 80 MHz.	Use Scenario: Conditioning millivolt-level outputs from thermocouples or strain gauges in PLC analog input modules. IC Role / Device Role / Timing Role: Discrete transistor in differential pair or current mirror configuration for precision current sourcing. Use Value: Tight h_FE spread (80–250) and −55°C to +150°C operating range ensure calibration stability across harsh factory environments.

Audio Preamplifier Stage

High-Voltage Switch Driver

Use Scenario: Amplifying weak signals from electret microphones or magnetic pickups before ADC sampling.

IC Role / Device Role / Timing Role: Discrete NPN transistor configured in common-emitter topology for voltage gain and impedance transformation.

Use Value: 8.0 dB noise figure and 200 MHz f_T preserve wideband fidelity while enabling single-stage gain >100 without oscillation risk.

Use Scenario: Driving relay coils or small solenoids from 5 V or 12 V microcontroller GPIO pins.

IC Role / Device Role / Timing Role: Saturated switch controlling inductive load current with minimal power loss.

Use Value: 0.25 V V_CE(sat) at 50 mA reduces heat generation by >40% versus older 2N2222 variants, extending reliability in cyclic duty applications.

RF Signal Buffer

Industrial Sensor Interface

Use Scenario: Isolating and buffering 27–100 MHz RF signals in amateur radio receiver front-ends.

IC Role / Device Role / Timing Role: Common-collector emitter-follower providing low-output-impedance drive without phase inversion.

Use Value: 20 pF C_ibo and 300 MHz f_T support stable unity-gain operation with <1 dB insertion loss up to 80 MHz.

Use Scenario: Conditioning millivolt-level outputs from thermocouples or strain gauges in PLC analog input modules.

IC Role / Device Role / Timing Role: Discrete transistor in differential pair or current mirror configuration for precision current sourcing.

Use Value: Tight h_FE spread (80–250) and −55°C to +150°C operating range ensure calibration stability across harsh factory environments.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC547B	V_CEO = 45 V, h_FE = 200–450, f_T = 300 MHz, TO-92 but lower voltage rating	Not suitable for >60 V supply rails; preferred only in low-voltage consumer electronics	Select BC547B only when supply voltage remains ≤30 V and higher h_FE tolerance is required.
MPSA42	V_CEO = 300 V, I_C = 500 mA, f_T = 50 MHz, TO-92 but slower and higher-voltage optimized	Better for 200 V+ flyback suppression; unsuitable for >50 MHz signal paths due to limited bandwidth	Choose MPSA42 when primary requirement is high-voltage blocking rather than RF gain or low-noise amplification.

Compared with BC547B and MPSA42, the 2N5551 uniquely balances 160 V breakdown, 300 MHz f_T, and 8.0 dB noise performance - making it the optimal choice for medium-voltage, medium-frequency analog signal conditioning where both headroom and bandwidth matter.

Availability

2N5551 is available at Aetrix Electronics and suitable for audio preamplifier stages, high-voltage switch drivers, RF signal buffers, and industrial sensor interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 2N5551 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 manufacturer specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The 2N5551 belongs to onsemi's legacy discrete transistor product line, engineered for reliability in general-purpose linear amplification and switching applications where proven performance, wide temperature operation, and mechanical interoperability are critical.

FAQ

What is the maximum collector-emitter voltage rating for the 2N5551?

The 2N5551 has a maximum collector-emitter voltage (V_CEO) rating of 160 Vdc under specified test conditions (I_C = 1.0 mAdc, I_B = 0). This rating is confirmed in the "Maximum Ratings" table and verified in the "Electrical Characteristics" section of the official onsemi datasheet (Rev. 4, March 2006). Exceeding this voltage risks permanent breakdown.

Is the 2N5551 suitable for low-noise audio amplification?

Yes, the 2N5551 is suitable for low-noise audio amplification, with a measured noise figure of 8.0 dB at I_C = 250 µA, V_CE = 5.0 Vdc, R_S = 1.0 kΩ, and f = 1.0 kHz. This value is explicitly listed in the "Electrical Characteristics" table and validated across production lots per onsemi's characterization methodology. Its 200 MHz f_T also supports wideband fidelity in preamp stages.

What package type does the 2N5551RLRPG variant use?

The 2N5551RLRPG uses the TO-92 package (Case 29-11), as confirmed in the "Ordering Information" table on page 5 of the onsemi datasheet. The "RLRPG" suffix denotes tape-and-reel packaging with Pb-free finish, while the underlying device remains mechanically identical to the standard TO-92 outline with E-B-C pin configuration.

How does the 2N5551 compare to the 2N5550 in terms of voltage ratings?

The 2N5551 offers higher voltage ratings than the 2N5550: V_CEO is 160 V versus 140 V, and V_CBO is 180 V versus 160 V. These values are directly specified in the "Maximum Ratings" and "Electrical Characteristics" tables of the shared datasheet. Both share identical package, pinout, and thermal specs, making the 2N5551 a direct upgrade for higher-voltage designs.

What is the thermal resistance from junction to ambient (R_JA) for the 2N5551 in TO-92 package?

The thermal resistance from junction to ambient (R_JA) for the 2N5551 in TO-92 package is 200 °C/W, as published in the "Thermal Characteristics" table of the onsemi datasheet. This value assumes standard JEDEC test conditions (single-layer PCB, no heatsink), and actual performance improves with added copper area or forced airflow.

2N5551 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 Long Body

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 600 mA

Voltage - Collector Emitter Breakdown (Max):: 160 V

Vce Saturation (Max) @ Ib, Ic:: 200mV @ 5mA, 50mA

Current - Collector Cutoff (Max):: 50nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 80 @ 10mA, 5V

Power - Max:: 625 mW

Frequency - Transition:: 300MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92 (TO-226)

2N5551 FAQ

1.How can I place an order for 2N5551 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N5551 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for 2N5551 reliable?

The price and inventory of 2N5551 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N5551 is usually 5 days.

3.What payment methods are accepted for 2N5551?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N5551 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N5551?

2N5551 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N5551 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for 2N5551?

For technical support, including 2N5551 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N5551 requirements.

6.How does Aetrix verify that 2N5551 is sourced from the original manufacturer or authorized distributors?

All 2N5551 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 2N5551 meets industry standards.

7.What is the process for return or replacement of 2N5551?

All 2N5551 units undergo pre-shipment inspection (PSI). If there is an issue with 2N5551, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The 2N5551 part is unused and in its original packaging.

Return procedure for 2N5551:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…