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

onsemi 2N4123RLRM

Name: 2N4123RLRM
Brand: onsemi
SKU: 2N4123RLRM
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N4123RLRM

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: 2N4123RLRM.pdf

Description:: TRANS NPN 30V 0.2A TO92

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2N4123RLRM from onsemi is an NPN silicon general-purpose transistor in TO-92 package, rated for 30 V_CEO, 200 mA continuous collector current, and 625 mW power dissipation at 25°C ambient. It delivers DC current gain (h_FE) of 50–120 at I_C = 2 mA/V_CE = 1 V, with f_T = 250 MHz and V_CE(sat) ≤ 0.3 V at I_C = 50 mA/I_B = 5 mA - used in low-voltage switching and small-signal amplification circuits.

For engineers reviewing the 2N4123RLRM datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92 mechanical compatibility, guaranteed h_FE range, V_CEO/V_CBO ratings, thermal resistance (R_JA = 200°C/W), and tape-and-reel packaging (2000 units) for automated assembly.

Technical Context

This discrete NPN bipolar junction transistor operates in linear amplification and saturated switching modes. Its design supports base-driven control with verified V_BE(sat) ≤ 0.95 V and noise figure ≤ 6.0 dB at 1 kHz/100 µA, enabling use in audio preamplifiers and digital logic interface stages.

Thermal performance is defined by R_JC = 83.3°C/W and R_JA = 200°C/W, with junction temperature range from −55°C to +150°C. Small-signal parameters include h_fe = 50–120 at 1 kHz, C_ibo ≤ 8.0 pF, and C_cb ≤ 4.0 pF - confirming suitability for RF-coupled and broadband analog signal paths up to ~250 MHz.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	30 Vdc - maximum collector-emitter voltage before breakdown under open-emitter condition; defines safe operating voltage headroom in switching applications.
I_C (continuous)	200 mAdc - maximum DC collector current without thermal derating; sets upper limit for load-driving capability in relay drivers or LED switches.
P_D @ T_A = 25°C	625 mW - total device power dissipation at room ambient; requires heatsinking or layout derating above 25°C (5.0 mW/°C).
h_FE	50–120 - DC current gain at I_C = 2 mA/V_CE = 1 V; ensures predictable base drive requirements in amplifier bias networks.
f_T	250 MHz - transition frequency at I_C = 10 mA/V_CE = 20 V; validates usable bandwidth in RF front-end and oscillator designs.
V_CE(sat)	≤ 0.3 V - collector-emitter saturation voltage at I_C = 50 mA/I_B = 5 mA; minimizes conduction loss in low-side switch configurations.
R_JA	200°C/W - junction-to-ambient thermal resistance; determines required PCB copper area or airflow for thermal management.

Pinout & Package

2N4123RLRM uses the standard TO-92 (Case 29-11) through-hole plastic package with straight leads and tape-and-reel delivery (2000 units). Dimensions comply with ANSI Y14.5M: body height 4.45–5.20 mm, lead pitch 2.54 mm, and seating plane tolerance per specification.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal in NPN configuration	Connected to ground or low-impedance return path; base-emitter junction forward-biased during turn-on.
2 (Base)	Control input for minority-carrier injection	Receives current-limited drive signal; determines collector current via h_FE relationship (I_C ≈ h_FE × I_B).
3 (Collector)	Current source terminal in NPN configuration	Connected to load and supply rail; carries amplified output current with minimal V_CE(sat) drop in switching mode.

Key Features

Feature	Design Value
Pb-free TO-92 package	RoHS-compliant construction with verified solderability and JEDEC-standard footprint for legacy through-hole assembly.
Guaranteed h_FE range	50–120 at I_C = 2 mA/V_CE = 1 V enables deterministic biasing without gain binning in production designs.
Low V_CE(sat)	≤ 0.3 V at I_C/I_B = 10 ensures <150 mW conduction loss at 500 mW load, improving efficiency in battery-powered switches.
High f_T	250 MHz allows stable operation in 10–50 MHz oscillator tanks and broadband preamp stages without external compensation.
Wide T_J range	−55°C to +150°C junction rating supports deployment in automotive under-hood and industrial control environments.

Applications

Audio Preamp Stage	Microcontroller GPIO Interface
Use Scenario: Amplifying microphone-level signals (1–10 mV) into line-level range (0.5–2 Vpp) prior to ADC sampling. IC Role / Device Role / Timing Role: Small-signal NPN amplifier in common-emitter configuration with emitter degeneration resistor. Use Value: Verified h_fe ≥ 50 at 1 kHz and NF ≤ 6.0 dB ensure SNR > 65 dB in 20 Hz–20 kHz band without active filtering.	Use Scenario: Level-shifting and current boosting between 3.3 V microcontroller outputs and 5 V/12 V peripheral loads (e.g., relays, solenoids). IC Role / Device Role / Timing Role: Saturated switch controlled by MCU GPIO with base resistor limiting I_B to 5 mA. Use Value: V_CE(sat) ≤ 0.3 V guarantees <150 mW power loss at 500 mW load, eliminating need for heat sinks in space-constrained PCBs.
RF Signal Coupling	Industrial Sensor Interface
Use Scenario: Buffering and impedance matching in 27 MHz ISM-band transmitter driver stages. IC Role / Device Role / Timing Role: Common-base amplifier providing low-input/high-output impedance transformation. Use Value: f_T = 250 MHz and C_ibo ≤ 8.0 pF enable stable gain >10 dB up to 50 MHz with minimal parasitic resonance.	Use Scenario: Converting 4–20 mA loop current signals to voltage for PLC analog inputs using precision shunt resistors. IC Role / Device Role / Timing Role: Linear-mode current mirror or emitter follower providing isolation and drive strength. Use Value: h_FE stability across −40°C to +85°C ensures <±2% gain drift over industrial temperature range.

Audio Preamp Stage

Microcontroller GPIO Interface

Use Scenario: Amplifying microphone-level signals (1–10 mV) into line-level range (0.5–2 Vpp) prior to ADC sampling.

IC Role / Device Role / Timing Role: Small-signal NPN amplifier in common-emitter configuration with emitter degeneration resistor.

Use Value: Verified h_fe ≥ 50 at 1 kHz and NF ≤ 6.0 dB ensure SNR > 65 dB in 20 Hz–20 kHz band without active filtering.

Use Scenario: Level-shifting and current boosting between 3.3 V microcontroller outputs and 5 V/12 V peripheral loads (e.g., relays, solenoids).

IC Role / Device Role / Timing Role: Saturated switch controlled by MCU GPIO with base resistor limiting I_B to 5 mA.

Use Value: V_CE(sat) ≤ 0.3 V guarantees <150 mW power loss at 500 mW load, eliminating need for heat sinks in space-constrained PCBs.

RF Signal Coupling

Industrial Sensor Interface

Use Scenario: Buffering and impedance matching in 27 MHz ISM-band transmitter driver stages.

IC Role / Device Role / Timing Role: Common-base amplifier providing low-input/high-output impedance transformation.

Use Value: f_T = 250 MHz and C_ibo ≤ 8.0 pF enable stable gain >10 dB up to 50 MHz with minimal parasitic resonance.

Use Scenario: Converting 4–20 mA loop current signals to voltage for PLC analog inputs using precision shunt resistors.

IC Role / Device Role / Timing Role: Linear-mode current mirror or emitter follower providing isolation and drive strength.

Use Value: h_FE stability across −40°C to +85°C ensures <±2% gain drift over industrial temperature range.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
2N4124RLRM	Lower V_CEO (25 V vs. 30 V) and V_CBO (30 V vs. 40 V); identical TO-92 package and pinout.	Suitable only where supply rails remain ≤ 22 V; not recommended for 24 V industrial systems requiring margin.	Select 2N4124RLRM only when lower voltage rating is acceptable and cost optimization is prioritized.
BC547B	Higher h_FE (200–450), same V_CEO (45 V), but different pinout (E-B-C vs. E-B-C for 2N4123RLRM) and package (TO-92 variant).	Requires PCB layout revision due to non-identical pin assignment; better for high-gain linear amplifiers than switching.	Choose BC547B only if higher gain is critical and board rework is feasible; not a drop-in replacement.

Compared with 2N4123RLRM, 2N4124RLRM offers identical form factor but reduced voltage margin, while BC547B provides superior gain at the cost of incompatible pin mapping - making 2N4123RLRM optimal for legacy TO-92 designs needing 30 V_CEO and proven thermal behavior.

Availability

2N4123RLRM is available at Aetrix Electronics and suitable for industrial sensor interfaces, microcontroller GPIO buffering, audio preamplification, and RF coupling circuits requiring stable component supply, consistent parametric performance, and RoHS-compliant through-hole assembly.

Supply support for 2N4123RLRM 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 management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The 2N4123RLRM belongs to onsemi's legacy general-purpose transistor product line, engineered for reliability in cost-sensitive, high-volume applications including control logic, signal conditioning, and discrete switching across diverse electronic systems.

FAQ

What is the maximum collector-emitter voltage rating for the 2N4123RLRM?

The 2N4123RLRM has a maximum collector-emitter voltage (V_CEO) rating of 30 Vdc under open-emitter conditions. This rating is validated per onsemi's published datasheet (Publication Order Number: 2N4123/D, Rev. 4) and defines the absolute upper limit for safe operation in switching or linear applications without risk of avalanche breakdown.

Does the 2N4123RLRM have a Pb-free package?

Yes, the 2N4123RLRM is supplied in a Pb-free TO-92 package compliant with RoHS Directive 2011/65/EU. The marking "2N4123RLRM" includes the "R" suffix indicating tape-and-reel packaging and the "L" suffix denoting lead-free construction, as confirmed in onsemi's ordering information and Pb-Free Strategy documentation.

What is the DC current gain (h_FE) range of the 2N4123RLRM at typical operating conditions?

The 2N4123RLRM exhibits a DC current gain (h_FE) range of 50 to 120 when measured at I_C = 2.0 mAdc and V_CE = 1.0 Vdc, per onsemi's Electrical Characteristics table. This range is guaranteed across production lots and supports robust bias network design without gain binning.

Can the 2N4123RLRM be used in RF amplifier applications?

Yes, the 2N4123RLRM is specified with a current-gain bandwidth product (f_T) of 250 MHz at I_C = 10 mAdc/V_CE = 20 Vdc, and small-signal h_fe ≥ 50 at 1 kHz. These parameters confirm usability in VHF oscillator and broadband amplifier stages up to approximately 50 MHz, provided layout minimizes stray capacitance.

What is the thermal resistance (junction-to-ambient) for the 2N4123RLRM in free-air conditions?

The 2N4123RLRM has a thermal resistance (R_JA) of 200°C/W when mounted on a standard FR-4 PCB with no added copper pour or heatsinking. This value is specified in the Thermal Characteristics section of the official datasheet and must be applied with derating (5.0 mW/°C above 25°C ambient) to maintain safe junction temperatures.

2N4123RLRM Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 200 mA

Voltage - Collector Emitter Breakdown (Max):: 30 V

Vce Saturation (Max) @ Ib, Ic:: 300mV @ 5mA, 50mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 50 @ 2mA, 1V

Power - Max:: 625 mW

Frequency - Transition:: 250MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

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

2N4123RLRM FAQ

1.How can I place an order for 2N4123RLRM through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N4123RLRM 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 2N4123RLRM reliable?

The price and inventory of 2N4123RLRM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N4123RLRM is usually 5 days.

3.What payment methods are accepted for 2N4123RLRM?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N4123RLRM transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N4123RLRM?

2N4123RLRM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N4123RLRM 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 2N4123RLRM?

For technical support, including 2N4123RLRM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N4123RLRM requirements.

6.How does Aetrix verify that 2N4123RLRM is sourced from the original manufacturer or authorized distributors?

All 2N4123RLRM 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 2N4123RLRM meets industry standards.

7.What is the process for return or replacement of 2N4123RLRM?

All 2N4123RLRM units undergo pre-shipment inspection (PSI). If there is an issue with 2N4123RLRM, 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 2N4123RLRM part is unused and in its original packaging.

Return procedure for 2N4123RLRM:

1.Submit a request within 90 days.

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

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