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

onsemi 2N5551RLRA

Name: 2N5551RLRA
Brand: onsemi
SKU: 2N5551RLRA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N5551RLRA

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: 2N5551RLRA.pdf

Description:: TRANS NPN 160V 0.6A TO92

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2N5551RLRA 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 T_A = 25°C. 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 2N5551RLRA datasheet, pinout, applications, or equivalent options, key selection criteria include its 160 V_CEO rating, 8.0 dB noise figure at 1 kHz, 6.0 pF C_obo, TO-92 mechanical compatibility, and Pb-free RLRA tape-and-reel packaging for automated assembly.

Technical Context

The 2N5551RLRA operates as a medium-voltage, medium-current NPN bipolar junction transistor optimized for linear amplification and fast switching. Its h_FE range spans 80–250 across I_C = 1–50 mA with V_CE = 5 V, and it achieves f_T = 100–300 MHz under I_C = 10 mA, V_CE = 10 V conditions.

Thermal performance is defined by R_JA = 200°C/W and R_JC = 83.3°C/W, supporting operation from −55°C to +150°C junction temperature. Saturation voltages are specified at V_CE(sat) ≤ 0.25 V (I_C/I_B = 10) and V_BE(sat) ≤ 1.2 V, enabling efficient low-loss switching in discrete driver stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	160 V - Maximum collector-emitter voltage before breakdown; enables use in 120 V rail switching and high-voltage analog stages.
I_C Continuous	600 mA - Sustained collector current handling; supports medium-power signal buffering and relay drivers.
h_FE Range	80–250 - DC current gain variation across 1–50 mA I_C; allows stable biasing in Class-A amplifiers without excessive gain spread.
f_T	100–300 MHz - Transition frequency at I_C = 10 mA; suitable for RF preamp and broadband audio applications up to ~100 MHz.
Noise Figure	8.0 dB @ 1 kHz - Low-noise performance at 250 μA I_C; critical for microphone preamps and sensor front-ends.
C_obo	6.0 pF - Output capacitance at V_CB = 10 V; limits high-frequency loading in tuned amplifier designs.
P_D @ T_A	625 mW - Power dissipation limit at 25°C ambient; requires heatsinking or derating above 25°C per 5.0 mW/°C slope.

Pinout & Package

2N5551RLRA uses the standard TO-92 (Case 29, Style 1) plastic package with 3-pin vertical lead configuration and Pb-free finish. Pin 1 is Emitter, Pin 2 is Base, Pin 3 is Collector - verified per onsemi marking diagram and package outline drawing.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current exit path for majority carriers	Reference node for bias network; connects to ground or emitter resistor in common-emitter configurations.
Pin 2 (Base)	Control terminal for carrier injection	Receives base drive current (I_B) to modulate I_C; requires current-limiting resistor in most switch/amplifier topologies.
Pin 3 (Collector)	Current entry path for majority carriers	Connects to load or supply rail; handles full output current and voltage swing in active/saturation regions.

Key Features

Feature	Design Value
High V_CBO	180 V - Enables robust operation in high-side switching and flyback snubber circuits without premature avalanche.
Low noise figure	8.0 dB @ 1 kHz - Reduces signal degradation in sensitive analog front-ends like electret microphone amplifiers.
Fast switching capability	t_r/t_f < 300 ns @ V_CC = 30 V - Supports PWM frequencies up to ~1 MHz in discrete gate drivers and LED dimmers.
Pb-free RLRA packaging	Tape-and-reel (2000 pcs) - Complies with RoHS and enables direct placement on SMT lines using standard TO-92 feeders.
Wide temperature range	−55°C to +150°C T_J - Validated for industrial control, automotive under-hood, and outdoor equipment environments.

Applications

Audio Preamplifier Stage	Switching Regulator Driver
Use Scenario: Low-noise amplification of electret microphone output prior to ADC sampling in voice-enabled IoT devices. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier operating in common-emitter configuration with emitter degeneration. Use Value: 8.0 dB noise figure and 250 h_FE at 1 mA enable >65 dB SNR in 20 Hz–20 kHz band without op-amp complexity.	Use Scenario: Driving the gate of a high-voltage MOSFET in a 48 V input buck converter with 500 kHz switching frequency. IC Role / Device Role / Timing Role: Medium-speed BJT switch providing current gain to overcome MOSFET gate charge requirements. Use Value: 300 ns turn-off time and 160 V_CEO rating ensure reliable dead-time control and voltage margin during transient spikes.
High-Voltage Signal Buffer	Discrete Logic Level Shifter
Use Scenario: Isolating and amplifying 0–10 V analog sensor signals in PLC analog input modules exposed to industrial noise. IC Role / Device Role / Timing Role: Common-collector emitter-follower buffer with 180 V_CBO headroom for transient suppression. Use Value: 600 mA I_C and low V_CE(sat) ≤ 0.25 V minimize output impedance and voltage droop under 10 mA load.	Use Scenario: Translating 3.3 V microcontroller GPIO outputs to 12 V logic levels for solenoid control in HVAC actuators. IC Role / Device Role / Timing Role: Saturated NPN switch with base resistor network defining logic threshold and drive strength. Use Value: Guaranteed h_FE ≥ 80 at I_C = 10 mA ensures full saturation with ≤120 μA base current, reducing MCU I/O loading.

Audio Preamplifier Stage

Switching Regulator Driver

Use Scenario: Low-noise amplification of electret microphone output prior to ADC sampling in voice-enabled IoT devices.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier operating in common-emitter configuration with emitter degeneration.

Use Value: 8.0 dB noise figure and 250 h_FE at 1 mA enable >65 dB SNR in 20 Hz–20 kHz band without op-amp complexity.

Use Scenario: Driving the gate of a high-voltage MOSFET in a 48 V input buck converter with 500 kHz switching frequency.

IC Role / Device Role / Timing Role: Medium-speed BJT switch providing current gain to overcome MOSFET gate charge requirements.

Use Value: 300 ns turn-off time and 160 V_CEO rating ensure reliable dead-time control and voltage margin during transient spikes.

High-Voltage Signal Buffer

Discrete Logic Level Shifter

Use Scenario: Isolating and amplifying 0–10 V analog sensor signals in PLC analog input modules exposed to industrial noise.

IC Role / Device Role / Timing Role: Common-collector emitter-follower buffer with 180 V_CBO headroom for transient suppression.

Use Value: 600 mA I_C and low V_CE(sat) ≤ 0.25 V minimize output impedance and voltage droop under 10 mA load.

Use Scenario: Translating 3.3 V microcontroller GPIO outputs to 12 V logic levels for solenoid control in HVAC actuators.

IC Role / Device Role / Timing Role: Saturated NPN switch with base resistor network defining logic threshold and drive strength.

Use Value: Guaranteed h_FE ≥ 80 at I_C = 10 mA ensures full saturation with ≤120 μA base current, reducing MCU I/O loading.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
2N5551G	Pb-free TO-92 in bulk (5000 units/box); identical electrical specs but different packaging format.	Suitable for manual prototyping or low-volume hand-soldered assemblies where tape-and-reel is unnecessary.	Select 2N5551G when evaluating circuit functionality without SMT line integration.
MPSA42	Higher V_CEO = 300 V, lower h_FE = 40–120, same TO-92 package; f_T = 50 MHz.	Better suited for high-voltage flyback snubbers and AC line sensing, but less optimal for low-noise audio due to higher NF.	Choose MPSA42 only when >200 V blocking is mandatory and gain/noise trade-offs are acceptable.

Compared with 2N5551RLRA, 2N5551G offers identical performance in a non-reel format ideal for bench validation, while MPSA42 trades bandwidth and noise performance for higher voltage tolerance-making it a functional alternative only in high-voltage, low-frequency contexts.

Availability

2N5551RLRA is available at Aetrix Electronics and suitable for audio preamplifier stages, switching regulator drivers, and high-voltage signal buffers requiring stable component supply, consistent Pb-free compliance, and TO-92 tape-and-reel logistics support.

Supply support for 2N5551RLRA 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 energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The 2N5551RLRA belongs to onsemi's legacy general-purpose bipolar transistor product line, designed for cost-sensitive, high-reliability linear amplification and switching applications across industrial controls and communications infrastructure.

FAQ

What is the maximum collector-emitter voltage rating for the 2N5551RLRA?

The 2N5551RLRA has a guaranteed minimum V_CEO rating of 160 Vdc, verified per onsemi's 2006 datasheet under I_C = 1.0 mAdc and I_B = 0 conditions. This rating defines the absolute maximum voltage the device can withstand between collector and emitter in open-base configuration without breakdown, and must be respected with appropriate safety margins in circuit design.

Is the 2N5551RLRA RoHS-compliant and what does "RLRA" signify in the part number?

Yes, the 2N5551RLRA is RoHS-compliant and features a Pb-free finish, as confirmed by onsemi's "G" suffix designation and RLRA packaging code. "RLRA" specifically denotes tape-and-reel packaging (2000 units per reel) in the standard TO-92 outline, optimized for automated SMT placement without requiring lead tinning or special flux profiles.

How does the DC current gain (h_FE) of the 2N5551RLRA vary with collector current?

The 2N5551RLRA exhibits h_FE = 80–250 depending on I_C: minimum 80 at I_C = 1.0 mAdc, 80–250 at I_C = 10 mAdc, and 30–250 at I_C = 50 mAdc (all at V_CE = 5.0 Vdc). This wide gain spread necessitates emitter degeneration or feedback in precision amplifier designs to stabilize operating point against unit-to-unit variation.

Can the 2N5551RLRA replace the 2N5550 in existing designs?

The 2N5551RLRA is not a direct drop-in replacement for the 2N5550 due to higher voltage ratings (V_CEO = 160 V vs. 140 V, V_CBO = 180 V vs. 160 V) and tighter h_FE distribution - though both share identical TO-92 pinout and thermal characteristics. Circuit validation is required if substituting into legacy 2N5550 designs, especially where gain stability or voltage margin affects reliability.

What is the thermal resistance from junction to ambient (R_JA) for the 2N5551RLRA in free-air conditions?

The 2N5551RLRA has a specified R_JA of 200°C/W under natural convection conditions on FR-4 PCB with no copper pour. This value implies a 200°C temperature rise per watt dissipated - so at its 625 mW maximum rated power, junction temperature will rise ~125°C above ambient, requiring careful layout or derating for sustained operation above 25°C ambient.

2N5551RLRA Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Reel (TR)

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)

2N5551RLRA FAQ

1.How can I place an order for 2N5551RLRA through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N5551RLRA 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 2N5551RLRA reliable?

The price and inventory of 2N5551RLRA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N5551RLRA is usually 5 days.

3.What payment methods are accepted for 2N5551RLRA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N5551RLRA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N5551RLRA?

2N5551RLRA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N5551RLRA 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 2N5551RLRA?

For technical support, including 2N5551RLRA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N5551RLRA requirements.

6.How does Aetrix verify that 2N5551RLRA is sourced from the original manufacturer or authorized distributors?

All 2N5551RLRA 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 2N5551RLRA meets industry standards.

7.What is the process for return or replacement of 2N5551RLRA?

All 2N5551RLRA units undergo pre-shipment inspection (PSI). If there is an issue with 2N5551RLRA, 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 2N5551RLRA part is unused and in its original packaging.

Return procedure for 2N5551RLRA:

1.Submit a request within 90 days.

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

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