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onsemi 2N4124BU
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- Part No.:
- 2N4124BU
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA)
- Datasheet:
-
2N4124BU.pdf
- Description:
- TRANS NPN 25V 0.2A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:6,674
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Product details
Overview
2N4124BU from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-to-medium power analog and digital circuits. It delivers DC current gain (hFE) of 120–360 at IC = 2 mA, supports 100 MHz bandwidth (fT), and handles continuous collector current up to 200 mA with VCEO = 25 V - commonly used in audio preamplifiers, signal conditioning stages, and discrete logic-level translators.
For engineers reviewing the 2N4124BU datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92 package compatibility, verified 300 MHz fT performance, low noise figure (5.0 dB at 10 Hz–15.7 kHz), saturation voltage (VCE(sat) ≤ 0.3 V at IC = 50 mA), and thermal resistance (RθJA = 200 °C/W on FR-4).
Technical Context
The 2N4124BU operates as a silicon NPN BJT with epitaxial base construction, optimized for linear amplification and fast-switching behavior. Its small-signal current gain (hfe) ranges from 120 to 480 at VCE = 10 V and IC = 2 mA, and it exhibits stable gain across temperature (−55°C to +150°C junction range).
It features low output capacitance (Cobo = 4.0 pF at VCB = 5 V) and input capacitance (Cibo = 8.0 pF at VBE = 0.5 V), supporting high-frequency operation up to its 300 MHz fT limit. Noise performance is characterized at 5.0 dB NF with RS = 1.0 kΩ, making it suitable for low-noise front-end amplification where signal integrity is critical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 25 V - maximum safe collector-emitter voltage before breakdown; defines rail headroom in amplifier/saturation designs. |
| IC (continuous) | 200 mA - usable collector current limit for sustained operation without thermal derating. |
| fT | 300 MHz - unity-gain bandwidth; enables RF amplification up to ~100 MHz with usable gain margin. |
| hFE (min/max) | 120 / 360 - DC current gain range at IC = 2 mA; impacts bias stability and stage gain predictability. |
| VCE(sat) | ≤ 0.3 V at IC = 50 mA, IB = 5 mA - low saturation voltage reduces conduction loss in switching applications. |
| RθJA | 200 °C/W - junction-to-ambient thermal resistance on standard FR-4 PCB; determines max power dissipation at ambient. |
| NF | 5.0 dB - noise figure at 100 µA, 5 V, 1 kHz–15.7 kHz; specifies suitability for low-noise audio/precision sensor amps. |
Pinout & Package
2N4124BU is housed in a through-hole TO-92 package (3-lead, epoxy molded), with standardized lead configuration: Collector (C), Base (B), Emitter (E), viewed from flat side with leads down and left-to-right order C–B–E.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Collector (C) | Main current sink terminal | Connected to higher-potential supply rail in common-emitter configurations; carries full load current. |
| Base (B) | Control input terminal | Receives drive current to modulate collector current; requires external bias network for stable DC operating point. |
| Emitter (E) | Current source/reference terminal | Typically grounded or connected to emitter resistor for feedback; sets reference potential for VBE control. |
Key Features
| Feature | Design Value |
|---|---|
| High fT bandwidth | 300 MHz - enables use in wideband amplifiers and RF driver stages up to 100 MHz. |
| Low VCE(sat) | ≤ 0.3 V - minimizes power loss and heat generation in saturated switch operation. |
| Low noise figure | 5.0 dB - supports high-fidelity signal amplification in microphone preamps and sensor interfaces. |
| Wide temperature range | −55°C to +150°C - ensures reliability in industrial, automotive under-hood, and outdoor electronics. |
| TO-92 mechanical compatibility | Standardized footprint - allows drop-in replacement in legacy designs using 2N3904/2N2222-class layouts. |
Applications
| Audio Preamp Stage | Discrete Logic Level Translator |
|---|---|
Use Scenario: Amplifying weak microphone or piezoelectric sensor signals before ADC sampling in portable instrumentation. IC Role / Device Role / Timing Role: NPN BJT configured in common-emitter topology with emitter degeneration for linearity and gain control. Use Value: 5.0 dB noise figure and 120–360 hFE enable >60 dB SNR at 1 kHz with minimal external components. | Use Scenario: Converting 3.3 V logic outputs to interface with 5 V TTL inputs in mixed-voltage microcontroller systems. IC Role / Device Role / Timing Role: Saturated switch providing low-impedance pull-down path with fast turn-on (<10 ns) and storage time <100 ns. Use Value: VCE(sat) ≤ 0.3 V and fT = 300 MHz ensure clean edge transitions and minimal voltage drop during active-low assertion. |
| Linear Voltage Regulator Pass Element | Industrial Sensor Signal Conditioning |
Use Scenario: Acting as series pass transistor in adjustable linear regulators requiring <200 mA output current. IC Role / Device Role / Timing Role: Current-controlled emitter follower delivering regulated output with thermal foldback via external sensing. Use Value: RθJA = 200 °C/W and TJ(max) = 150°C support 625 mW dissipation at 25°C ambient - sufficient for 5 V @ 100 mA with 3 V dropout. | Use Scenario: Buffering and amplifying millivolt-level thermocouple or strain gauge outputs in PLC analog input modules. IC Role / Device Role / Timing Role: High-input-impedance common-collector (emitter-follower) stage isolating sensitive sensors from downstream loading. Use Value: hie ≈ 1–10 kΩ (frequency-dependent) and low Cibo (8.0 pF) preserve signal fidelity while rejecting capacitive coupling noise. |
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 |
|---|---|---|---|
| 2N3904 | Lower fT (300 MHz vs 300 MHz nominal, but typically 250–270 MHz), slightly lower hFE min (100 vs 120), same TO-92 package. | Marginally reduced high-frequency gain stability above 50 MHz; otherwise functionally interchangeable in DC/low-MHz apps. | Select 2N3904 only if cost sensitivity outweighs need for guaranteed 300 MHz fT and tighter hFE binning. |
| BC547B | Higher VCEO (45 V), similar hFE range (200–450), but Cobo = 4.5 pF and RθJA = 250 °C/W - less efficient thermal performance. | Better voltage headroom for 12–24 V systems; higher thermal resistance limits power handling in compact enclosures. | Choose BC547B when operating above 25 V supply rails or when sourcing from European distributors with strong BC547 inventory. |
Compared with 2N3904 and BC547B, the 2N4124BU offers superior thermal efficiency (RθJA = 200 °C/W), guaranteed 300 MHz fT, and tighter hFE consistency - making it preferred for precision analog gain stages and high-reliability industrial signal chains where parameter spread must be minimized.
Availability
2N4124BU is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic level translators, and industrial sensor signal conditioning requiring stable component supply and long-term manufacturability.
Supply support for 2N4124BU 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
Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices, acquired by ON Semiconductor in 2016.
The 2N4124BU belongs to Fairchild's legacy general-purpose BJT family, engineered for robustness, predictable gain, and broad operating temperature support in industrial and consumer analog signal paths.
FAQ
What is the maximum operating junction temperature for the 2N4124BU?
The 2N4124BU has a maximum operating junction temperature (TJ) of +150°C, as specified in its Absolute Maximum Ratings table. This rating assumes proper PCB thermal design - including adequate copper area and airflow - and derating of power dissipation above 25°C ambient per its 5.0 mW/°C thermal derating curve. Exceeding this temperature risks permanent degradation of hFE and increased leakage.
Is the 2N4124BU pin-compatible with the 2N3904?
Yes, the 2N4124BU uses the same TO-92 package and identical C–B–E pinout as the 2N3904, enabling direct physical replacement in existing PCB footprints. However, the 2N4124BU provides higher minimum hFE (120 vs 100) and guaranteed 300 MHz fT, so circuit performance may improve - especially in gain-critical or high-frequency applications - without layout changes.
What is the typical noise figure of the 2N4124BU and under what conditions is it measured?
The 2N4124BU has a typical noise figure (NF) of 5.0 dB, measured at IC = 100 µA, VCE = 5.0 V, RS = 1.0 kΩ, and over the frequency band 10 Hz to 15.7 kHz. This value reflects its suitability for low-noise preamplifier stages in audio and sensor signal chains where preserving signal-to-noise ratio is essential.
Can the 2N4124BU be used in switching applications, and what are its key switching parameters?
Yes, the 2N4124BU is qualified for switching use, with VCE(sat) ≤ 0.3 V at IC = 50 mA / IB = 5 mA and typical turn-on time <10 ns. Its storage time and fall time remain below 100 ns at IC = 10 mA, supporting clean digital transitions up to ~10 MHz. For reliable switching, ensure base drive meets required IB/IC ratio and avoid operation near absolute maximum ratings.
Does the 2N4124BU have any automotive or AEC-Q200 qualification?
No, the 2N4124BU is not AEC-Q200 qualified or automotive-grade rated. It is specified for commercial and industrial temperature ranges (−55°C to +150°C), but lacks the extended life testing, lot traceability, and failure rate validation required for automotive applications. For automotive use, consider ON Semiconductor's NSS40201MR6T1G or other AEC-Q101-qualified NPN transistors instead of the 2N4124BU.
2N4124BU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 200 mA
- Voltage - Collector Emitter Breakdown (Max):
- 25 V
- Vce Saturation (Max) @ Ib, Ic:
- 300mV @ 5mA, 50mA
- Current - Collector Cutoff (Max):
- 50nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 120 @ 2mA, 1V
- Power - Max:
- 625 mW
- Frequency - Transition:
- 300MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
2N4124BU FAQ
1.How can I place an order for 2N4124BU through Aetrix?
Please submit a Request for Quotation (RFQ) for 2N4124BU 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 2N4124BU reliable?
The price and inventory of 2N4124BU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N4124BU is usually 5 days.
3.What payment methods are accepted for 2N4124BU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N4124BU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 2N4124BU?
2N4124BU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 2N4124BU 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 2N4124BU?
For technical support, including 2N4124BU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N4124BU requirements.
6.How does Aetrix verify that 2N4124BU is sourced from the original manufacturer or authorized distributors?
All 2N4124BU 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 2N4124BU meets industry standards.
7.What is the process for return or replacement of 2N4124BU?
All 2N4124BU units undergo pre-shipment inspection (PSI). If there is an issue with 2N4124BU, 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 2N4124BU part is unused and in its original packaging.
Return procedure for 2N4124BU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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