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onsemi FJX945GTF-ON
- Part No.:
- FJX945GTF-ON
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- SC-70, SOT-323
- Datasheet:
-
FJX945GTF-ON.pdf
- Description:
- TRANS NPN 50V 0.15A SOT-323
- Quantity:
- Payment:
- Shipping:
Inventory:6,000
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Product details
Overview
FJX945GTF-ON from onsemi (formerly Fairchild Semiconductor) is an NPN epitaxial silicon transistor designed for audio frequency amplification and high-frequency oscillator circuits. It features VCBO=60 V, VCEO=50 V, IC=150 mA, fT=300 MHz (typ), and hFE=70–700 (grade-dependent), operating in SOT-323 package with 3-pin surface-mount configuration.
For engineers reviewing the FJX945GTF-ON datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain range (O/Y/G/L grades), saturation voltage at IC=100 mA/IB=10 mA, noise figure of 4.0 dB at 1 kHz, Cob=2.5 pF, and thermal limits up to TJ=150°C.
Technical Context
This NPN bipolar junction transistor uses epitaxial base construction to achieve high fT and low noise performance. Its breakdown voltages (VCBO=60 V, VCEO=50 V, VEBO=5 V) support moderate-voltage analog signal stages, while the 300 MHz fT enables stable operation in RF oscillator and broadband amplifier designs up to VHF.
The device exhibits graded hFE bins (O: 70–140, Y: 120–240, G: 200–400, L: 350–700) and low saturation voltage (VCE(sat) ≤ 0.3 V at IC=100 mA/IB=10 mA), making it suitable for linear amplification and switching where gain consistency and low conduction loss are critical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | 60 V - Maximum reverse bias voltage between collector and base before breakdown; sets upper limit for common-base amplifier headroom. |
| VCEO | 50 V - Maximum collector-emitter voltage under open-base condition; defines safe operating voltage in common-emitter configurations. |
| fT | 300 MHz (typ) - Current gain bandwidth product; supports stable small-signal amplification up to ~100 MHz with adequate gain margin. |
| hFE | 70–700 (grade-dependent) - DC current gain range across O/Y/G/L classifications; enables precise biasing selection for gain-stable amplifier design. |
| VCE(sat) | ≤0.3 V at IC=100 mA/IB=10 mA - Low saturation voltage ensures minimal power loss and heat generation in switching applications. |
| Cob | 2.5 pF at VCB=6 V - Output capacitance limits high-frequency gain roll-off and affects stability in tuned RF circuits. |
| NF | 4.0 dB at 1 kHz - Measured noise figure with RS=500 Ω; indicates suitability for low-noise preamplifier stages in audio systems. |
Pinout & Package
SOT-323 (SC-70) 3-pin surface-mount plastic package: compact footprint (2.00 × 1.25 mm), low thermal resistance, and standard tape-and-reel delivery for automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Base) | Control electrode | Receives input drive current to modulate collector current; requires external bias network for stable Q-point setting. |
| 2 (Emitter) | Current source terminal | Common reference node in common-emitter/common-base topologies; connects to ground or emitter degeneration resistor. |
| 3 (Collector) | Output current terminal | Delivers amplified output current; connects to load resistor or RF tank circuit depending on application topology. |
Key Features
| Feature | Design Value |
|---|---|
| High fT performance | 300 MHz typical - Enables reliable operation in VHF oscillator and broadband amplifier designs without external neutralization. |
| Graded hFE bins | O/Y/G/L classifications - Allows production matching of gain-critical stages without post-manufacture sorting or trimming. |
| Low noise figure | 4.0 dB at 1 kHz - Supports high-fidelity audio preamplification with minimal added signal degradation. |
| Complementary pairing | Designed as NPN complement to FJX733 PNP - Enables push-pull and differential pair implementations with matched characteristics. |
| SOT-323 packaging | Standardized 3-pin SC-70 footprint - Ensures compatibility with high-density PCB layouts and reflow soldering processes. |
Applications
| Audio Preamp Stage | RF Local Oscillator |
|---|---|
Use Scenario: Low-noise voltage amplification of microphone or line-level signals prior to ADC conversion. IC Role / Device Role / Timing Role: NPN small-signal amplifier in common-emitter configuration with emitter degeneration. Use Value: 4.0 dB noise figure and hFE ≥ 200 (G-grade) ensure high SNR and stable gain control in battery-powered portable audio devices. | Use Scenario: Fundamental-mode LC oscillator generating 10–50 MHz clock signals for IF mixing or local tuning. IC Role / Device Role / Timing Role: Active gain element in Colpitts or Clapp oscillator topology. Use Value: 300 MHz fT and 2.5 pF Cob enable robust oscillation startup and frequency stability with minimal phase noise contribution. |
| Switching Regulator Driver | Signal Coupling Amplifier |
Use Scenario: Base drive stage for medium-current power switches in DC-DC converter feedback loops. IC Role / Device Role / Timing Role: Current buffer between PWM controller output and MOSFET gate. Use Value: VCE(sat) ≤ 0.3 V at 100 mA reduces driver-stage conduction loss and improves overall converter efficiency. | Use Scenario: AC-coupled gain block between sensor interface and analog front-end in industrial measurement systems. IC Role / Device Role / Timing Role: Linear amplifier with fixed bias and capacitive coupling on input/output. Use Value: 50 V VCEO and 150 mA IC rating allow safe operation with ±15 V rails and transient-tolerant signal swing handling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN small-signal transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MMBT918LT1G | fT = 700 MHz (higher), VCEO = 30 V (lower), SOT-23 package | Better high-frequency gain but reduced voltage headroom; unsuitable for >30 V collector supply rails | Select when fT > 500 MHz is required and VCEO ≤ 30 V suffices |
| BC847BW | hFE = 200–450 (narrower bin), VCEO = 45 V, Cob = 4.5 pF (higher) | Higher output capacitance degrades VHF stability; tighter hFE range simplifies bias design but reduces gain flexibility | Prefer for cost-sensitive consumer applications where 45 V rating and moderate fT suffice |
Compared with MMBT918LT1G and BC847BW, the FJX945GTF-ON offers superior voltage capability (50 V VCEO), balanced fT (300 MHz), and graded hFE bins-making it optimal for industrial audio and mid-VHF oscillator designs requiring both headroom and gain control.
Availability
FJX945GTF-ON is available at Aetrix Electronics and suitable for audio preamplifiers, RF local oscillators, switching regulator drivers, and signal coupling amplifiers requiring stable component supply and consistent parametric grading.
Supply support for FJX945GTF-ON 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 Fairchild Semiconductor) is a global semiconductor supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.
The FJX945GTF-ON belongs to Fairchild's legacy "FACT Quiet Series™" of low-noise, high-speed bipolar transistors, engineered specifically for high-fidelity audio and stable RF oscillator circuits.
FAQ
What is the maximum collector current rating for FJX945GTF-ON?
The FJX945GTF-ON has a maximum continuous collector current (IC) rating of 150 mA at Ta = 25°C. Derating is required above 25°C ambient per the thermal resistance curve in the datasheet. This rating ensures reliable operation in linear amplification and switching roles without exceeding the 200 mW collector power dissipation limit.
Does FJX945GTF-ON have a specified junction temperature limit?
Yes, the FJX945GTF-ON specifies a maximum junction temperature (TJ) of 150°C. This limit governs thermal design margins when operating at elevated ambient temperatures or under sustained power dissipation. The SOT-323 package's thermal resistance (RθJA ≈ 350°C/W) must be considered alongside PCB copper area to maintain TJ ≤ 150°C in actual layouts.
How does the hFE grading (O/Y/G/L) affect FJX945GTF-ON selection?
The FJX945GTF-ON is binned into four hFE ranges: O (70–140), Y (120–240), G (200–400), and L (350–700). Grade selection directly impacts bias stability and gain predictability-G or L grades are preferred for low-distortion audio amplifiers, while O or Y may suit switching applications where precise gain is less critical. Each FJX945GTF-ON unit is marked with its specific grade letter.
Is FJX945GTF-ON pin-compatible with other SOT-323 NPN transistors?
The FJX945GTF-ON uses standard SOT-323 pinout (1=Base, 2=Emitter, 3=Collector), matching industry convention for 3-pin SC-70 packages. While mechanical fit is assured, electrical compatibility depends on parameters like VCEO, fT, and hFE-so direct substitution requires verification against target circuit requirements. The FJX945GTF-ON is explicitly designed as complement to FJX733, not as generic drop-in replacement.
What is the typical noise figure of FJX945GTF-ON and under what conditions is it measured?
The FJX945GTF-ON has a typical noise figure (NF) of 4.0 dB, measured at VCE = 6 V, IE = −0.5 mA, f = 1 kHz, and RS = 500 Ω. This value reflects its suitability for low-noise preamplifier stages in audio signal chains, where minimizing added noise is essential to preserve signal integrity before digitization or further processing.
FJX945GTF-ON Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- SC-70, SOT-323
- Packaging:
- Bulk
- Product Status:
- Active
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 150 mA
- Voltage - Collector Emitter Breakdown (Max):
- 50 V
- Vce Saturation (Max) @ Ib, Ic:
- 300mV @ 10mA, 100mA
- Current - Collector Cutoff (Max):
- 100nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 200 @ 1mA, 6V
- Power - Max:
- 200 mW
- Frequency - Transition:
- 300MHz
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-323
FJX945GTF-ON FAQ
1.How can I place an order for FJX945GTF-ON through Aetrix?
Please submit a Request for Quotation (RFQ) for FJX945GTF-ON 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 FJX945GTF-ON reliable?
The price and inventory of FJX945GTF-ON are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FJX945GTF-ON is usually 5 days.
3.What payment methods are accepted for FJX945GTF-ON?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FJX945GTF-ON transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FJX945GTF-ON?
FJX945GTF-ON orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FJX945GTF-ON 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 FJX945GTF-ON?
For technical support, including FJX945GTF-ON datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FJX945GTF-ON requirements.
6.How does Aetrix verify that FJX945GTF-ON is sourced from the original manufacturer or authorized distributors?
All FJX945GTF-ON 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 FJX945GTF-ON meets industry standards.
7.What is the process for return or replacement of FJX945GTF-ON?
All FJX945GTF-ON units undergo pre-shipment inspection (PSI). If there is an issue with FJX945GTF-ON, 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 FJX945GTF-ON part is unused and in its original packaging.
Return procedure for FJX945GTF-ON:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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