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onsemi 2N4126TFR
- Part No.:
- 2N4126TFR
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
2N4126TFR.pdf
- Description:
- TRANS PNP 25V 0.2A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:9,105
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Product details
Overview
2N4126TFR from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor (BJT) designed for low-to-medium current amplification and switching in discrete analog and digital circuits, with confirmed VCEO = 25 V, IC = 200 mA continuous, hFE = 120–360 at 2 mA, and TO-92 package. It serves in signal conditioning stages of industrial sensor interfaces, power supply enable/disable logic, and low-speed digital output drivers.
For engineers reviewing the 2N4126TFR datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, guaranteed fT ≥ 250 MHz, thermal resistance RθJA = 200 °C/W on FR-4, and compatibility with through-hole prototyping and legacy board layouts.
Technical Context
The 2N4126TFR operates as a single PNP BJT with fixed emitter-base-collector terminal assignment and no integrated biasing or protection circuitry. Its DC current gain (hFE) exhibits strong collector-current dependence-120 min at IC = 2 mA and 60 min at IC = 50 mA-indicating optimized use in linear amplification below 10 mA or saturated switching above 10 mA.
Small-signal behavior is characterized by fT = 250 MHz at IC = 10 mA/VCE = 20 V, Cibo = 10 pF at VEB = 0.5 V, and NF = 4.0 dB at IC = 100 µA/RS = 1 kΩ, confirming suitability for audio-frequency amplification and low-noise preamplifier stages where bandwidth and noise floor are critical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 25 V - Maximum safe voltage between collector and emitter with base open; defines upper rail limit in PNP switch or amplifier stage. |
| IC (continuous) | 200 mA - Absolute max DC collector current; usable up to 100 mA for reliable thermal margin on standard FR-4 PCB. |
| hFE @ 2 mA | 120–360 - High DC gain enables low-base-drive designs in linear amplifiers and low-power switches. |
| fT | 250 MHz - Unity-gain bandwidth supports stable operation up to ~50 MHz in common-emitter configurations. |
| RθJA | 200 °C/W - Thermal resistance on 1.6" × 1.6" FR-4; limits power dissipation to ≤350 mW at 75°C ambient without heatsinking. |
| VBE(sat) | 0.95 V @ IC/IB = 50 mA/5 mA - Confirmed saturation voltage ensures predictable turn-on threshold in logic-level interface applications. |
| NF | 4.0 dB @ 10 Hz–15.7 kHz - Measured noise figure qualifies 2N4126TFR for microphone preamp and sensor signal-chain front ends. |
Pinout & Package
2N4126TFR is supplied in the TO-92 through-hole plastic package (JEDEC TO-92 variant), with standardized lead configuration: flat side facing viewer, leads downward, left-to-right pin order E-B-C (Emitter-Base-Collector). The package supports manual soldering, wave soldering, and socket-based testing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| E (Emitter) | Current source terminal for PNP device | Connected to higher potential rail (e.g., VCC) in common-emitter amplifier; must be DC-biased above base for conduction. |
| B (Base) | Control input node | Receives negative-going drive signal relative to emitter; requires current-limiting resistor to set IB and ensure saturation or linear operation. |
| C (Collector) | Current sink terminal | Connected to load and lower-potential node (e.g., GND); voltage swing limited by VCEO = 25 V and saturation drop VCE(sat) ≤ 0.4 V. |
Key Features
| Feature | Design Value |
|---|---|
| High hFE range | 120–360 at low IC enables precise gain control and reduced base drive requirements in analog stages. |
| Low VCE(sat) | ≤0.4 V at IC/IB = 50 mA/5 mA minimizes conduction loss in power-switching applications. |
| 250 MHz fT | Supports wideband amplification up to audio and low-RF frequencies without external compensation. |
| 4.0 dB noise figure | Validated at 100 µA bias, making it suitable for low-level signal amplification before ADC input stages. |
| TO-92 mechanical standardization | Ensures plug-and-play compatibility with legacy test fixtures, breadboards, and production tooling. |
Applications
| Industrial Sensor Signal Conditioning | Linear Voltage Regulator Pass Element |
|---|---|
|
Use Scenario: Amplifying millivolt-level outputs from thermocouples or strain gauges into 0–5 V ranges for microcontroller ADC input. IC Role / Device Role / Timing Role: PNP BJT configured as common-emitter DC-coupled amplifier with emitter degeneration resistor. Use Value: High hFE and low NF preserve signal integrity while enabling single-transistor gain stages without op-amps. |
Use Scenario: Serving as the series pass element in a discrete adjustable linear regulator delivering 12 V @ 150 mA to analog subsystems. IC Role / Device Role / Timing Role: PNP transistor operating in active region, controlled by error amplifier feedback loop. Use Value: VCEO = 25 V and IC = 200 mA allow safe operation with 24 V input rails and moderate load currents. |
| Microcontroller Output Driver | Power Supply Enable/Disable Switch |
|
Use Scenario: Inverting logic-level translation from 3.3 V MCU GPIO to drive 5 V/12 V relays or LEDs with >100 mA load current. IC Role / Device Role / Timing Role: PNP switch in common-emitter configuration, base driven via current-limiting resistor. Use Value: Verified VBE(sat) = 0.95 V and VCE(sat) = 0.4 V ensure predictable turn-on and minimal voltage drop under load. |
Use Scenario: Enabling/disabling downstream 5 V LDO regulators in multi-rail embedded systems using MCU-controlled PNP high-side switch. IC Role / Device Role / Timing Role: PNP transistor used as high-side switch with base pulled low to activate. Use Value: TO-92 package and robust IC rating support direct integration into compact power management sections without layout redesign. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PNP general-purpose amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MMBT4126 | SOT-23 surface-mount package; identical electrical specs (VCEO, hFE, fT, NF) per shared datasheet. | Requires reflow-compatible layout; unsuitable for through-hole prototyping or hand-soldered repairs. | Select MMBT4126 only when board space constraints mandate SMT and assembly supports 0.95 mm pitch. |
| 2N3906 | Lower IC = 200 mA (same), but hFE = 100–300 (min 100 vs. 120), fT = 250 MHz (same), RθJA = 357 °C/W (vs. 200 °C/W). | Higher thermal resistance reduces usable power at elevated ambient; lower hFE min increases base drive sensitivity. | Choose 2N3906 only if TO-92 footprint compatibility is required and thermal headroom exceeds 30°C above ambient. |
Compared with 2N4126TFR, MMBT4126 offers identical performance in a smaller SMT package but sacrifices serviceability and prototyping flexibility, while 2N3906 trades thermal efficiency and guaranteed low-current gain for broader industry availability and second-source assurance.
Availability
2N4126TFR is available at Aetrix Electronics and suitable for industrial sensor interfaces, linear regulator pass elements, and microcontroller output drivers requiring stable component supply across long-lifecycle embedded programs.
Supply support for 2N4126TFR 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 manufacturer specializing in discrete power devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.
The 2N4126TFR belongs to Fairchild's legacy general-purpose BJT product line, engineered for cost-sensitive, reliability-critical linear and switching functions in industrial and consumer electronics.
FAQ
What is the maximum continuous collector current rating for the 2N4126TFR?
The 2N4126TFR has a maximum continuous collector current (IC) rating of 200 mA at TA = 25°C, derated linearly above 25°C per its 5.0 mW/°C specification. For sustained operation at 100 mA, ambient temperature must remain below 75°C on standard FR-4 PCB to maintain junction temperature within the −55°C to +150°C range.
Is the 2N4126TFR pin-compatible with the 2N3906?
No, the 2N4126TFR and 2N3906 are not pin-compatible: both use TO-92 packages but differ in lead assignment-2N4126TFR follows E-B-C (flat side facing, left-to-right), whereas 2N3906 uses E-C-B. Swapping them without board revision causes functional failure due to reversed collector/emitter connections.
Does the 2N4126TFR support high-frequency amplification?
Yes, the 2N4126TFR delivers fT = 250 MHz at IC = 10 mA/VCE = 20 V, enabling stable small-signal amplification up to approximately 50 MHz in properly compensated common-emitter configurations. Its Cibo = 10 pF and Ccb = 4.5 pF further support RF-adjacent applications like IF stages in AM receivers.
What is the typical noise figure of the 2N4126TFR and under what conditions is it measured?
The 2N4126TFR has a typical noise figure (NF) of 4.0 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 is validated in the official Fairchild datasheet and confirms suitability for low-noise preamplifier roles in sensor signal chains prior to digitization.
Can the 2N4126TFR be used in switching power supply feedback loops?
Yes, the 2N4126TFR is suitable for optocoupler-driven feedback loops in isolated DC-DC converters, where its VCEO = 25 V withstands typical auxiliary winding voltages and its hFE stability across temperature ensures consistent current transfer ratio (CTR) compensation. Its TO-92 form factor also simplifies manual calibration during prototype validation.
2N4126TFR 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:
- PNP
- Current - Collector (Ic) (Max):
- 200 mA
- Voltage - Collector Emitter Breakdown (Max):
- 25 V
- Vce Saturation (Max) @ Ib, Ic:
- 400mV @ 5mA, 50mA
- Current - Collector Cutoff (Max):
- 50nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 120 @ 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
2N4126TFR FAQ
1.How can I place an order for 2N4126TFR through Aetrix?
Please submit a Request for Quotation (RFQ) for 2N4126TFR 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 2N4126TFR reliable?
The price and inventory of 2N4126TFR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N4126TFR is usually 5 days.
3.What payment methods are accepted for 2N4126TFR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N4126TFR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 2N4126TFR?
2N4126TFR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 2N4126TFR 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 2N4126TFR?
For technical support, including 2N4126TFR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N4126TFR requirements.
6.How does Aetrix verify that 2N4126TFR is sourced from the original manufacturer or authorized distributors?
All 2N4126TFR 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 2N4126TFR meets industry standards.
7.What is the process for return or replacement of 2N4126TFR?
All 2N4126TFR units undergo pre-shipment inspection (PSI). If there is an issue with 2N4126TFR, 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 2N4126TFR part is unused and in its original packaging.
Return procedure for 2N4126TFR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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