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

onsemi 2N4123TA

Name: 2N4123TA
Brand: onsemi
SKU: 2N4123TA
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N4123TA

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: 2N4123TA.pdf

Description:: TRANS NPN 30V 0.2A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2N4123TA from ON Semiconductor (formerly Fairchild) is an NPN general-purpose bipolar junction transistor used for low-power amplification and switching in analog and digital circuits, with V_CEO = 30 V, I_C = 200 mA continuous, h_FE = 50–150 at I_C = 2 mA, f_T = 250 MHz, and TO-92 package. It serves in signal conditioning stages of audio preamps, logic-level translators, and low-current load switches.

For engineers reviewing the 2N4123TA datasheet, pinout, applications, or equivalent options, key selection considerations include its DC current gain range, saturation voltage under 50 mA drive, thermal resistance (R_θJA = 200 °C/W), noise figure (6.0 dB at 100 µA), and suitability for discrete amplifier stages requiring stable h_FE across –40°C to +125°C.

Technical Context

The 2N4123TA operates as a silicon NPN BJT with epitaxial base construction optimized for high-frequency small-signal amplification and reliable switching up to 100 mA collector current. Its f_T of 250 MHz and h_fe ≥ 2.5 at 100 MHz confirm usable RF performance in IF and low-VHF applications.

It features low output capacitance (C_ob = 4.0 pF at V_CB = 5 V) and input capacitance (C_ib = 8.0 pF at V_EB = 0.5 V), enabling fast switching with t_r, t_f, and t_s in the nanosecond range under defined test conditions. The device supports operation from –55°C to +150°C junction temperature with derated power dissipation above 25°C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	30 V - Maximum safe collector-emitter voltage before breakdown; sets upper rail limit for common-emitter amplifier stages.
I_C (continuous)	200 mA - Continuous collector current handling; supports driving relays, LEDs, or small MOSFET gates without heatsinking.
h_FE	50–150 @ I_C = 2 mA - DC current gain range defining base drive requirements for linear or saturated operation.
f_T	250 MHz - Unity-gain frequency; enables use in 20–50 MHz RF amplifiers and high-speed pulse circuits.
NF	6.0 dB @ 100 µA, 10 Hz–15.7 kHz - Low-noise capability suitable for microphone preamplifier input stages.
R_θJA	200 °C/W - Junction-to-ambient thermal resistance in TO-92; limits power dissipation to ≤625 mW at 25°C ambient.

Pinout & Package

2N4123TA is housed in a through-hole TO-92 package (3-lead, straight-lead variant), with standard lead orientation when viewed from flat side: Emitter (left), Base (center), Collector (right).

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current sink terminal	Reference node for biasing; connects to ground or low-impedance return path in common-emitter configurations.
Base (B)	Control input	Receives current-limited drive to modulate collector current; requires series resistor to limit I_B and prevent saturation overshoot.
Collector (C)	Current source terminal	Delivers amplified output current; connects to load and supply rail in switching or active-load amplifier topologies.

Key Features

Feature	Design Value
High f_T / low C_ob combination	250 MHz f_T with only 4.0 pF output capacitance enables stable gain up to 50 MHz without neutralization.
Wide operating temperature range	Junction temperature support from –55°C to +150°C allows deployment in industrial and automotive under-hood environments.
Low V_BE(sat)	0.95 V @ I_C = 50 mA ensures minimal base drive voltage overhead in logic-compatible switching designs.
Controlled h_FE spread	Guaranteed 50–150 h_FE binning enables predictable biasing without individual transistor trimming in production assemblies.

Applications

Audio Preamp Stage	Logic-Level Translator
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors into line-level outputs. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier configured in common-emitter topology with emitter degeneration. Use Value: 6.0 dB noise figure and 50–150 h_FE ensure high SNR and consistent gain across production units without feedback trimming.	Use Scenario: Converting 3.3 V CMOS logic outputs to interface with 5 V TTL inputs in mixed-voltage systems. IC Role / Device Role / Timing Role: Saturated switch translating logic states with sub-100 ns propagation delay and rail-to-rail output swing. Use Value: V_CE(sat) ≤ 0.3 V at I_C/I_B = 10 ensures clean low-state definition and minimal power loss during switching.
LED Driver	Relay Driver
Use Scenario: Driving single or parallel strings of indicator LEDs from microcontroller GPIO pins. IC Role / Device Role / Timing Role: Constant-current switch controlling LED anode/cathode current via base-resistor-limited I_B. Use Value: 200 mA I_C rating and 0.95 V V_BE(sat) allow direct drive of up to 100 mA LEDs with 3.3 V MCU logic without level-shifting.	Use Scenario: Activating 5–12 V electromagnetic relays in PLC I/O modules and industrial control panels. IC Role / Device Role / Timing Role: High-gain saturated switch providing galvanic isolation between control logic and relay coil. Use Value: 30 V V_CEO and 625 mW P_D accommodate typical 12 V/40 mA relay coils with margin for inductive kickback suppression.

Audio Preamp Stage

Logic-Level Translator

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors into line-level outputs.

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

Use Value: 6.0 dB noise figure and 50–150 h_FE ensure high SNR and consistent gain across production units without feedback trimming.

Use Scenario: Converting 3.3 V CMOS logic outputs to interface with 5 V TTL inputs in mixed-voltage systems.

IC Role / Device Role / Timing Role: Saturated switch translating logic states with sub-100 ns propagation delay and rail-to-rail output swing.

Use Value: V_CE(sat) ≤ 0.3 V at I_C/I_B = 10 ensures clean low-state definition and minimal power loss during switching.

LED Driver

Relay Driver

Use Scenario: Driving single or parallel strings of indicator LEDs from microcontroller GPIO pins.

IC Role / Device Role / Timing Role: Constant-current switch controlling LED anode/cathode current via base-resistor-limited I_B.

Use Value: 200 mA I_C rating and 0.95 V V_BE(sat) allow direct drive of up to 100 mA LEDs with 3.3 V MCU logic without level-shifting.

Use Scenario: Activating 5–12 V electromagnetic relays in PLC I/O modules and industrial control panels.

IC Role / Device Role / Timing Role: High-gain saturated switch providing galvanic isolation between control logic and relay coil.

Use Value: 30 V V_CEO and 625 mW P_D accommodate typical 12 V/40 mA relay coils with margin for inductive kickback suppression.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
PN2222A	Higher V_CEO (40 V), lower f_T (300 MHz typ. but not guaranteed), wider h_FE spread (100–300)	Better suited for higher-voltage switching; less consistent gain in linear amplifiers due to wider h_FE distribution	Choose PN2222A when V_CEO > 30 V is required; verify h_FE binning if gain stability is critical.
BC547C	Lower I_C (100 mA), smaller TO-92 footprint, tighter h_FE binning (420–800 for 'C' grade)	Optimized for low-current, high-gain small-signal amplification; unsuitable for >100 mA loads	Choose BC547C for battery-powered sensor amps where gain precision matters more than current drive.

Compared with PN2222A and BC547C, the 2N4123TA offers balanced performance: sufficient voltage headroom (30 V), verified 250 MHz f_T, and moderate h_FE consistency-making it ideal for cost-sensitive, medium-current analog and switching functions where both gain predictability and frequency response matter.

Availability

2N4123TA is available at Aetrix Electronics and suitable for audio preamplifiers, logic-level translators, LED drivers, and relay drivers requiring stable component supply across industrial, instrumentation, and consumer electronics programs.

Supply support for 2N4123TA 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 manufacturer specializing in power management, analog, sensors, and discrete devices, with legacy roots in Fairchild Semiconductor's discrete portfolio.

The 2N4123TA belongs to ON Semiconductor's general-purpose bipolar transistor product line, designed for cost-effective, reliable amplification and switching in non-critical analog and digital signal paths across commercial and industrial equipment.

FAQ

What is the maximum continuous collector current rating for the 2N4123TA?

The 2N4123TA has a maximum continuous collector current (I_C) rating of 200 mA at T_A = 25°C. This rating decreases with rising ambient temperature per the specified derating curve (5.0 mW/°C above 25°C), and actual usable current depends on PCB copper area, airflow, and thermal interface. For sustained 100 mA operation, ensure junction temperature remains below 150°C using R_θJA = 200 °C/W.

Does the 2N4123TA have a guaranteed minimum h_FE at high collector currents?

Yes-the 2N4123TA guarantees h_FE ≥ 25 at I_C = 50 mA and V_CE = 1.0 V, per its datasheet ON CHARACTERISTICS table. This ensures predictable base drive requirements even under moderate saturation conditions, supporting robust switching behavior in relay and LED driver designs without excessive overdrive.

Can the 2N4123TA be used in RF amplifier stages?

Yes-the 2N4123TA has a specified f_T of 250 MHz and low parasitic capacitances (C_ob = 4.0 pF, C_ib = 8.0 pF), making it suitable for narrowband RF amplification up to ~50 MHz. Its noise figure of 6.0 dB at 100 µA also supports low-noise front-end use in AM/FM receiver IF stages, provided proper biasing and impedance matching networks are implemented.

What is the pin configuration of the 2N4123TA in TO-92 package?

When viewing the 2N4123TA TO-92 package with the flat side facing you and leads pointing downward, the pin order from left to right is: Emitter (E), Base (B), Collector (C). This matches JEDEC TO-92 standard orientation and is confirmed in Fairchild's original 2N4123 datasheet Rev A. No alternate pinouts are specified for this part number.

Is the 2N4123TA RoHS compliant and halogen-free?

Yes-the 2N4123TA is RoHS compliant and halogen-free, as documented in ON Semiconductor's official packaging and environmental compliance reports. It meets EU Directive 2011/65/EU and contains <900 ppm bromine and <900 ppm chlorine, with no intentionally added halogenated flame retardants. Full material declarations are available upon request for qualified customers.

2N4123TA Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Packaging:: Tape & Box (TB)

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-92-3

2N4123TA FAQ

1.How can I place an order for 2N4123TA through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N4123TA 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 2N4123TA reliable?

The price and inventory of 2N4123TA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N4123TA is usually 5 days.

3.What payment methods are accepted for 2N4123TA?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N4123TA transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N4123TA?

2N4123TA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N4123TA 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 2N4123TA?

For technical support, including 2N4123TA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N4123TA requirements.

6.How does Aetrix verify that 2N4123TA is sourced from the original manufacturer or authorized distributors?

All 2N4123TA 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 2N4123TA meets industry standards.

7.What is the process for return or replacement of 2N4123TA?

All 2N4123TA units undergo pre-shipment inspection (PSI). If there is an issue with 2N4123TA, 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 2N4123TA part is unused and in its original packaging.

Return procedure for 2N4123TA:

1.Submit a request within 90 days.

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

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