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onsemi FJX945GTF
- Part No.:
- FJX945GTF
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- SC-70, SOT-323
- Datasheet:
-
FJX945GTF.pdf
- Description:
- TRANS NPN 50V 0.15A SOT-323
- Quantity:
- Payment:
- Shipping:
Inventory:4,578
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Product details
Overview
FJX945GTF from ON Semiconductor is an NPN epitaxial silicon transistor in SOT-323 package, rated for 60 V VCBO, 50 V VCEO, and 150 mA IC, with fT = 300 MHz (typ) and hFE = 70–700 (grade-dependent), used in audio frequency amplification and high-frequency oscillator circuits.
For engineers reviewing the FJX945GTF datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain range, saturation voltage at 100 mA/10 mA drive, noise figure at 1 kHz, output capacitance at 6 V, and thermal limits up to 150 °C junction temperature.
Technical Context
This discrete NPN transistor features a planar epitaxial structure optimized for RF and audio switching/amplification. Its 300 MHz fT enables stable operation in VHF oscillator and preamplifier stages, while low Cob (2.5 pF at 6 V) supports minimal signal loss in tuned circuits.
The device exhibits graded hFE bins (O/Y/G/L) spanning 70–700, allowing precision biasing across production lots. Complementarity with FJX733 (PNP counterpart) supports push-pull and differential pair designs without layout redesign.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | 60 V - maximum reverse bias before collector-base breakdown; defines safe headroom in common-emitter switch applications |
| VCEO | 50 V - maximum collector-emitter voltage under open-base condition; sets upper rail limit in amplifier stages |
| IC | 150 mA - continuous collector current rating; determines usable output swing in Class-A audio drivers |
| fT | 300 MHz (typ) - unity-gain bandwidth at VCE = 6 V, IC = 10 mA; confirms suitability for 27–108 MHz FM oscillator use |
| hFE | 70–700 (grade-dependent) - DC current gain range per bin; enables tailored bias stability across production batches |
| Cob | 2.5 pF at VCB = 6 V - output capacitance limiting high-frequency roll-off in tuned collector loads |
| NF | 4.0 dB at 1 kHz, RS = 500 Ω - noise floor relevant for low-level audio preamp input stages |
Pinout & Package
SOT-323 surface-mount plastic package (2.00 × 1.25 × 0.90 mm), lead-free and RoHS-compliant, with gull-wing leads for reflow compatibility and thermal dissipation up to 200 mW.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Base) | Control electrode | Accepts forward-biased current to modulate collector conduction; requires series resistor for stable bias in linear operation |
| 2 (Emitter) | Current source terminal | Connected to ground or low-impedance node; forms reference for base-emitter voltage drop and emitter degeneration |
| 3 (Collector) | Output current terminal | Delivers amplified current to load; must be decoupled from supply in RF applications to prevent oscillation |
Key Features
| Feature | Design Value |
|---|---|
| High fT performance | 300 MHz typical gain-bandwidth enables stable oscillation up to 100 MHz without external compensation |
| Graded hFE bins | O/Y/G/L classifications allow matched-pair selection or consistent DC operating point targeting across volume production |
| Low noise figure | 4.0 dB at 1 kHz supports high-SNR audio preamplification where input signal integrity is critical |
| Complementary PNP pairing | Designed as direct complement to FJX733, enabling symmetrical push-pull output stages without redesign |
Applications
| FM Radio Front-End Amplifier | Portable Audio Preamp Stage |
|---|---|
Use Scenario: Low-noise amplification of 88–108 MHz RF signals prior to mixer stage in compact FM receivers. IC Role / Device Role / Timing Role: NPN RF amplifier configured in common-emitter topology with tuned collector load. Use Value: 300 MHz fT and 2.5 pF Cob ensure minimal insertion loss and stable gain across FM band without neutralization. | Use Scenario: First-stage voltage amplification of microphone or line-level signals in battery-powered audio recorders. IC Role / Device Role / Timing Role: Linear Class-A small-signal amplifier with emitter degeneration for distortion control. Use Value: 4.0 dB NF and wide hFE range enable low-distortion, high-SNR amplification with minimal quiescent power draw. |
| Crystal Oscillator Buffer | LED Driver Switch |
Use Scenario: Isolation and gain restoration of 1–10 MHz crystal oscillator outputs driving multiple downstream logic loads. IC Role / Device Role / Timing Role: Emitter-follower buffer providing low-impedance output while preserving waveform integrity. Use Value: High hFE (up to 700) and low VCE(sat) (0.15 V typ) minimize propagation delay and loading effects on crystal tank. | Use Scenario: Digital on/off control of indicator LEDs in space-constrained industrial HMI panels. IC Role / Device Role / Timing Role: Saturated-switch NPN driver with base current limiting for predictable turn-on/turn-off behavior. Use Value: 150 mA IC rating and 0.3 V max VCE(sat) ensure full LED brightness with <100 mW dissipation in SOT-323 footprint. |
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 |
|---|---|---|---|
| MMBT918 | fT = 700 MHz (higher), VCEO = 30 V (lower), SOT-23 package | Better for >100 MHz RF but unsuitable for 50 V rail applications | Select when higher speed outweighs voltage margin; verify PCB pad compatibility |
| BC847B | hFE = 200–450 (narrower bin), VCEO = 45 V, same SOT-323 footprint | Lower max voltage and tighter gain spread reduce design margin in variable-bias circuits | Prefer for cost-sensitive consumer audio where 45 V rail suffices and bin consistency is prioritized |
Compared with MMBT918 and BC847B, the FJX945GTF delivers superior voltage headroom (50 V VCEO) and broader hFE flexibility (70–700), making it optimal for industrial-grade oscillator and amplifier designs requiring both robustness and bias adaptability.
Availability
FJX945GTF is available at Aetrix Electronics and suitable for FM radio front-end amplifiers, portable audio preamps, crystal oscillator buffers, and LED driver switches requiring stable component supply and long-term manufacturability.
Supply support for FJX945GTF 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 supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and edge applications.
The FJX945GTF belongs to Fairchild's legacy FACT Quiet Series™ small-signal transistor family, engineered for low-noise, high-speed analog and RF signal conditioning in space-constrained portable systems.
FAQ
What is the maximum collector-emitter voltage rating for the FJX945GTF?
The FJX945GTF has a maximum collector-emitter voltage (VCEO) rating of 50 V at Ta = 25 °C. This rating applies under open-base conditions and defines the absolute upper limit for DC or peak AC voltage across the collector and emitter terminals. Exceeding this value risks irreversible breakdown. Derating is required at elevated temperatures per the datasheet's thermal curves. The FJX945GTF must not be operated beyond 50 V VCEO in any circuit configuration.
Does the FJX945GTF have a specified noise figure, and under what conditions is it measured?
Yes, the FJX945GTF has a specified noise figure of 4.0 dB, measured at VCE = 6 V, IE = −0.5 mA, f = 1 kHz, and RS = 500 Ω. This value reflects its performance in low-frequency, low-level amplification tasks such as microphone preamplification. The measurement assumes proper biasing and source impedance matching; actual noise in a given design depends on layout, decoupling, and surrounding component tolerances. The FJX945GTF's 4.0 dB NF is confirmed in the original Fairchild datasheet Rev. B2.
What is the pin configuration of the FJX945GTF in the SOT-323 package?
The FJX945GTF uses a standard SOT-323 pinout: Pin 1 is Base, Pin 2 is Emitter, and Pin 3 is Collector - viewed from top with marking dot at top-left corner. This arrangement matches JEDEC MO-203-DA and is identical to industry-standard NPN SOT-323 transistors. No alternate pinouts exist for this part number. The FJX945GTF's pin mapping is explicitly shown in the "Package Dimensions" section of its datasheet, confirming mechanical and electrical alignment with common SMT assembly processes.
How does the hFE grading (O/Y/G/L) affect selection of the FJX945GTF for circuit design?
The FJX945GTF is binned into four hFE ranges: O (70–140), Y (120–240), G (200–400), and L (350–700). This grading allows designers to select units matching specific bias requirements - e.g., L-grade for high-gain, low-base-current amplifiers; O-grade for stable, low-drift switching. Each grade maintains identical absolute maximum ratings and thermal specs. The FJX945GTF's hFE bin is marked on the package (e.g., "SAX" for grade L), enabling traceability and repeatable performance across production runs.
Is the FJX945GTF a direct replacement for the FJX733 transistor?
No - the FJX945GTF is an NPN transistor and the FJX733 is its complementary PNP counterpart; they are not interchangeable. However, the FJX945GTF is explicitly designed as the NPN complement to the FJX733 in push-pull, differential, or mirror configurations. Their matching VCEO, fT, and package (SOT-323) enable symmetrical circuit implementation. Substituting FJX945GTF for FJX733 would invert circuit polarity and cause functional failure. The FJX945GTF and FJX733 are paired components, not drop-in replacements.
FJX945GTF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- SC-70, SOT-323
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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 FAQ
1.How can I place an order for FJX945GTF through Aetrix?
Please submit a Request for Quotation (RFQ) for FJX945GTF 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 reliable?
The price and inventory of FJX945GTF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FJX945GTF is usually 5 days.
3.What payment methods are accepted for FJX945GTF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FJX945GTF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FJX945GTF?
FJX945GTF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FJX945GTF 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?
For technical support, including FJX945GTF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FJX945GTF requirements.
6.How does Aetrix verify that FJX945GTF is sourced from the original manufacturer or authorized distributors?
All FJX945GTF 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 meets industry standards.
7.What is the process for return or replacement of FJX945GTF?
All FJX945GTF units undergo pre-shipment inspection (PSI). If there is an issue with FJX945GTF, 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 part is unused and in its original packaging.
Return procedure for FJX945GTF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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