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onsemi 2N4124TFR
- Part No.:
- 2N4124TFR
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
2N4124TFR.pdf
- Description:
- TRANS NPN 25V 0.2A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:5,039
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Product details
Overview
2N4124TFR from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor designed for low-power amplification and switching in discrete analog and digital circuits. It delivers DC current gain (hFE) of 120–360 at IC = 2 mA, supports 100 MHz current-gain bandwidth (fT), withstands 25 V VCEO, and operates across –55°C to +150°C junction temperature range - commonly deployed in signal conditioning stages of industrial sensor interfaces and low-speed logic buffers.
For engineers reviewing the 2N4124TFR datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package thermal resistance (RθJA = 200°C/W), saturation voltage (VCE(sat) = 0.3 V at IC = 50 mA), noise figure (NF = 5.0 dB), and compatibility with legacy through-hole amplifier designs requiring proven reliability and wide temperature operation.
Technical Context
The 2N4124TFR is a silicon NPN BJT optimized for linear amplification and saturated switching. Its fT = 300 MHz enables stable small-signal gain up to VHF frequencies, while hfe = 120–480 at 1 kHz confirms high transconductance in audio and IF stages. The device uses planar epitaxial construction with gold-doped base region to balance speed and ruggedness.
Thermal design relies on FR-4 PCB mounting (1.6" × 1.6" × 0.06") per JEDEC standards; RθJA = 200°C/W and maximum PD = 625 mW at 25°C define safe continuous bias limits. Cobo = 4.0 pF and Cibo = 8.0 pF support predictable high-frequency impedance matching without external neutralization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 25 V - Maximum collector-emitter voltage before breakdown; sets safe operating voltage ceiling for common-emitter switch/amplifier configurations. |
| hFE (IC = 2 mA) | 120–360 - DC current gain range defining minimum base drive needed for reliable saturation in switching applications. |
| fT | 300 MHz - Current-gain bandwidth product; determines usable small-signal amplification limit without phase inversion or gain roll-off. |
| VCE(sat) | 0.3 V @ IC = 50 mA - Low saturation voltage reduces conduction loss and self-heating in digital logic interface and relay driver circuits. |
| NOISE FIGURE | 5.0 dB @ IC = 100 µA - Quantifies added noise in low-level signal amplification; suitable for preamplifier stages in instrumentation front-ends. |
| RθJA | 200 °C/W - Junction-to-ambient thermal resistance on standard FR-4 board; used to calculate max ambient temperature for 150°C junction limit. |
| Operating TJ | –55°C to +150°C - Wide junction temperature range enables deployment in automotive under-hood and industrial control environments. |
Pinout & Package
2N4124TFR is supplied in the industry-standard TO-92 plastic package (3-lead, upright, epoxy-molded), with leads arranged in straight-line configuration and pin 1 = Emitter, pin 2 = Base, pin 3 = Collector when viewed with flat side facing user and leads downward.
| 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 topology. |
| Base (B) | Control input | Receives forward-biased current to modulate collector current; requires series resistor to limit IB and prevent thermal runaway. |
| Collector (C) | Current source terminal | Delivers amplified output current; connects to load or next stage; must remain below VCEO rating under all operating conditions. |
Key Features
| Feature | Design Value |
|---|---|
| High fT / low Cobo synergy | 300 MHz fT with only 4.0 pF output capacitance enables stable RF amplification without peaking or instability in tuned circuits. |
| Low-noise amplification | 5.0 dB noise figure at 100 µA allows use in microphone preamps and sensor signal chains where SNR preservation is critical. |
| Wide temperature operation | –55°C to +150°C junction range supports deployment in unregulated enclosures and harsh industrial environments without derating. |
| Proven TO-92 reliability | JEDEC-compliant TO-92 package with 200°C/W RθJA provides consistent thermal performance across decades of field use in legacy equipment. |
Applications
| Audio Pre-amplifier Stage | Industrial Sensor Interface |
|---|---|
Use Scenario: Amplifying low-level signals from electret microphones or piezoelectric sensors before ADC sampling. IC Role / Device Role / Timing Role: Discrete NPN amplifier in common-emitter configuration with emitter degeneration for linearity and gain stability. Use Value: 5.0 dB noise figure and hfe ≥ 120 ensure minimal signal degradation and sufficient gain margin at 100 µA–2 mA bias points. |
Use Scenario: Conditioning millivolt-level outputs from RTDs, thermocouples, or strain gauges in PLC analog input modules. IC Role / Device Role / Timing Role: Transimpedance or differential pair amplifier providing gain and offset adjustment prior to isolation. Use Value: Stable hFE over –55°C to +150°C ensures calibration retention across environmental extremes without active compensation. |
| Digital Logic Level Shifter | Relay Driver Circuit |
Use Scenario: Converting 3.3 V CMOS logic outputs to 5 V or 12 V compatible levels for legacy microcontroller peripherals. IC Role / Device Role / Timing Role: Saturated switch with base resistor limiting IB to achieve β = 10 for fast turn-on/turn-off. Use Value: VCE(sat) = 0.3 V at IC = 50 mA minimizes power dissipation and heat rise during sustained ON-state operation. |
Use Scenario: Driving 5–24 V coil relays in HVAC controllers and motor starter panels. IC Role / Device Role / Timing Role: High-current switch with flyback diode protection, operated in hard saturation mode. Use Value: IC = 200 mA absolute max rating and 625 mW PD allow brief surge currents typical during relay pull-in without thermal stress. |
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 |
|---|---|---|---|
| MMBT4124 | SOT-23 surface-mount package; RθJA = 357°C/W; same electrical specs but lower power dissipation (350 mW). | Preferred for space-constrained PCBs; unsuitable for >150 mW continuous loads due to thermal limitation. | Select MMBT4124 when board area is constrained and peak power < 150 mW; retain 2N4124TFR for through-hole assembly or higher thermal mass requirements. |
| 2N3904 | Lower fT (300 MHz vs 300 MHz nominal, but typically 250–270 MHz); hFE min = 100; VCEO = 40 V; RθJA = 200°C/W. | Better voltage headroom; slightly reduced high-frequency gain consistency; widely available with tighter hFE bins. | Choose 2N3904 for designs needing >25 V collector swing or standardized hFE grading; 2N4124TFR preferred where specified fT and noise performance are critical. |
Compared with MMBT4124 and 2N3904, the 2N4124TFR offers identical fT and superior noise figure in a robust TO-92 package, making it optimal for repair, legacy replacement, and thermally demanding analog signal paths where SMT thermal limits are prohibitive.
Availability
2N4124TFR is available at Aetrix Electronics and suitable for industrial sensor interfaces, audio pre-amplifier stages, and relay driver circuits requiring stable component supply and long-term obsolescence resilience.
Supply support for 2N4124TFR 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 before its acquisition by ON Semiconductor in 2016; its legacy BJT portfolio remains widely deployed and supported.
The 2N4124TFR belongs to Fairchild's general-purpose NPN transistor family, engineered for broad utility in amplification and switching across consumer, industrial, and automotive electronics - emphasizing reliability, temperature stability, and ease of integration in discrete designs.
FAQ
What is the maximum continuous collector current for the 2N4124TFR?
The 2N4124TFR has an absolute maximum continuous collector current (IC) rating of 200 mA at TA = 25°C. Derating is required above 25°C per the 5.0 mW/°C thermal coefficient. For sustained operation near this limit, PCB copper area and ambient airflow must be verified against the RθJA = 200°C/W specification to avoid exceeding the 150°C maximum junction temperature.
Does the 2N4124TFR support high-frequency amplification up to 100 MHz?
Yes, the 2N4124TFR is characterized for useful dynamic range up to 100 MHz as an amplifier, with a typical current-gain bandwidth product (fT) of 300 MHz at IC = 10 mA and VCE = 20 V. Its small-signal hfe remains ≥120 up to 10 MHz, supporting stable gain in IF and low-VHF stages when properly biased and matched.
Is the 2N4124TFR pin-compatible with the 2N3904?
No, the 2N4124TFR and 2N3904 are not pin-compatible: both use TO-92 packages but differ in lead assignment - 2N4124TFR has E-B-C (pin 1–2–3), while 2N3904 uses E-C-B. Swapping them without board modification will result in incorrect biasing and potential device failure. Always verify pinout diagrams before substitution.
What is the typical noise figure of the 2N4124TFR and under what conditions is it measured?
The 2N4124TFR has a typical noise figure of 5.0 dB, measured at IC = 100 µA, VCE = 5.0 V, RS = 1.0 kΩ, and frequency range 10 Hz to 15.7 kHz. This value reflects its suitability for low-noise pre-amplification in audio and sensor signal chains where preserving signal integrity at microvolt levels is essential.
Can the 2N4124TFR be used in switching applications with fast turn-on/turn-off requirements?
Yes, the 2N4124TFR supports switching applications with documented turn-on time < 500 ns, rise time < 100 ns, and fall time < 500 ns at IC = 10 mA. Its low VCE(sat) = 0.3 V and moderate storage time enable efficient operation in low-to-medium speed digital buffers and pulse generators up to ~1 MHz.
2N4124TFR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Packaging:
- Tape & Reel (TR)
- 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
2N4124TFR FAQ
1.How can I place an order for 2N4124TFR through Aetrix?
Please submit a Request for Quotation (RFQ) for 2N4124TFR 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 2N4124TFR reliable?
The price and inventory of 2N4124TFR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N4124TFR is usually 5 days.
3.What payment methods are accepted for 2N4124TFR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N4124TFR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 2N4124TFR?
2N4124TFR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 2N4124TFR 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 2N4124TFR?
For technical support, including 2N4124TFR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N4124TFR requirements.
6.How does Aetrix verify that 2N4124TFR is sourced from the original manufacturer or authorized distributors?
All 2N4124TFR 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 2N4124TFR meets industry standards.
7.What is the process for return or replacement of 2N4124TFR?
All 2N4124TFR units undergo pre-shipment inspection (PSI). If there is an issue with 2N4124TFR, 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 2N4124TFR part is unused and in its original packaging.
Return procedure for 2N4124TFR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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