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onsemi FJX945YTF
- Part No.:
- FJX945YTF
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- SC-70, SOT-323
- Datasheet:
-
FJX945YTF.pdf
- Description:
- TRANS NPN 50V 0.15A SOT-323
- Quantity:
- Payment:
- Shipping:
Inventory:6,094
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Product details
Overview
FJX945YTF 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), designed for audio frequency amplification and high-frequency oscillator circuits.
For engineers reviewing the FJX945YTF datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain range (grade Y: 120–240), saturation voltage (VCE(sat) ≤ 0.3 V at IC = 100 mA/IB = 10 mA), noise figure (4.0 dB at 1 kHz), output capacitance (2.5 pF), and SOT-323 thermal and layout constraints.
Technical Context
The FJX945YTF operates as a general-purpose RF/NPN switching and amplification device with verified breakdown voltages (BVCBO = 60 V, BVCEO = 50 V) and low leakage (ICBO ≤ 0.1 µA at VCB = 40 V). Its 300 MHz fT and 2.5 pF Cob support stable operation up to VHF band in tuned amplifier and oscillator topologies.
Grade Y classification specifies hFE = 120–240 at VCE = 6 V and IC = 1.0 mA, enabling predictable biasing in linear stages. Complementarity with FJX733 (PNP counterpart) allows matched-pair use in push-pull or differential configurations without external matching.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | 60 V - supports collector-base reverse bias up to 60 V without avalanche conduction |
| VCEO | 50 V - maximum safe collector-emitter voltage under open-base conditions |
| IC | 150 mA - continuous collector current rating defining small-signal switching/amplifier headroom |
| fT | 300 MHz (typ) - usable gain-bandwidth limit for RF amplification up to ~100 MHz with margin |
| hFE (Grade Y) | 120–240 - validated DC current gain range enabling stable bias design in Class-A amplifiers |
| VCE(sat) | ≤ 0.3 V at IC = 100 mA / IB = 10 mA - ensures low conduction loss in saturated-switch applications |
| Noise Figure | 4.0 dB at 1 kHz - suitable for low-noise preamplifier stages in audio signal chains |
Pinout & Package
Package: SOT-323 (SC-70), surface-mount, 3-pin plastic package with 1.25 mm × 2.10 mm footprint and 0.95 mm height; optimized for high-density PCB layouts and automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Base) | Control electrode | Receives base current to modulate collector-emitter conduction; requires current-limiting resistor in digital switch or bias network |
| 2 (Emitter) | Current source reference | Common terminal for emitter-grounded amplifier configurations; connects to ground or emitter degeneration resistor |
| 3 (Collector) | Output current path | Delivers amplified/saturated output current; routed to load or next stage with minimal trace inductance for RF stability |
Key Features
| Feature | Design Value |
|---|---|
| High fT performance | 300 MHz typical - enables stable amplification in VHF oscillator and IF amplifier designs |
| Low output capacitance | 2.5 pF at VCB = 6 V - minimizes Miller effect and improves high-frequency gain flatness |
| Grade-specific hFE binning | Y grade = 120–240 - reduces circuit calibration effort in production-grade audio preamps |
| Complementary pairing | Matched with FJX733 (PNP) - supports balanced differential and push-pull topologies without discrete matching |
| Low noise figure | 4.0 dB at 1 kHz - meets SNR requirements for microphone preamplifier and sensor interface stages |
Applications
| Audio Preamp Stage | RF Local Oscillator |
|---|---|
Use Scenario: Low-noise amplification of electret microphone or piezoelectric sensor signals prior to ADC sampling. 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 120–240 hFE ensure consistent gain and minimal added noise across production batches. | Use Scenario: Colpitts or Hartley oscillator core generating 20–80 MHz local oscillator signals for AM/FM receivers. IC Role / Device Role / Timing Role: Active gain element sustaining oscillation via tuned LC tank feedback. Use Value: 300 MHz fT and 2.5 pF Cob enable reliable start-up and frequency stability within target band. |
| Switch-Mode LED Driver | Signal-Level Translator |
Use Scenario: Constant-current switching driver for indicator LEDs in industrial HMI panels with 3.3 V logic control. IC Role / Device Role / Timing Role: Saturated NPN switch turning LED on/off with <0.3 V drop at 100 mA load. Use Value: Low VCE(sat) minimizes power dissipation and thermal rise in compact enclosures. | Use Scenario: Level-shifting interface between 3.3 V microcontroller GPIO and 5 V legacy peripheral bus lines. IC Role / Device Role / Timing Role: Inverting voltage translator with fixed gain and fast edge response. Use Value: 300 MHz fT ensures sub-10 ns propagation delay and clean signal integrity at 1–5 MHz toggle rates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MMBT3904LT1G | hFE = 100–300 (SOT-23); fT = 300 MHz; VCEO = 40 V; higher ICBO (50 nA) | Lower VCEO limits use in 50 V rail systems; wider hFE spread increases bias sensitivity | Select when SOT-23 footprint compatibility is required and 40 V VCEO suffices |
| BC847BW | hFE = 200–450 (SOT-323); fT = 100 MHz; VCEO = 45 V; higher Cob (4.5 pF) | Lower fT and higher capacitance reduce suitability for >30 MHz oscillator use | Select for cost-sensitive audio gain stages where bandwidth beyond 10 MHz is unnecessary |
Compared with MMBT3904LT1G and BC847BW, the FJX945YTF offers superior VCEO margin (50 V), tighter hFE binning for Grade Y (120–240), and lower Cob-making it preferred for 50 V-tolerant RF oscillator and low-noise preamp designs in space-constrained SOT-323 layouts.
Availability
FJX945YTF is available at Aetrix Electronics and suitable for audio preamplifiers, RF local oscillators, LED drivers, and level translators requiring stable component supply and consistent grade-Y hFE performance.
Supply support for FJX945YTF 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The FJX945YTF belongs to Fairchild's legacy "FACT Quiet Series™" discrete transistor line, engineered for low-noise, high-fT performance in compact SOT-323 packages for portable and high-density signal-chain applications.
FAQ
What is the hFE range for FJX945YTF?
The FJX945YTF is binned to Grade Y, specifying a DC current gain (hFE) range of 120–240 at VCE = 6 V and IC = 1.0 mA. This tight binning reduces variation in bias point design across production units and supports repeatable performance in audio amplifier and oscillator circuits without individual calibration.
Does FJX945YTF have a complementary PNP part?
Yes, the FJX945YTF has a documented complementary PNP counterpart: the FJX733. Both devices share matching package (SOT-323), voltage ratings, and gain-bandwidth characteristics, enabling direct use in push-pull, differential pair, and complementary symmetry amplifier topologies without external matching components.
What is the maximum operating temperature for FJX945YTF?
The FJX945YTF has a maximum junction temperature (TJ) of 150°C and a storage temperature range of –55°C to +150°C. Its SOT-323 package delivers thermal resistance (RθJA) of approximately 260°C/W, so derating is required above ~100 mW power dissipation in still-air environments to maintain safe TJ.
Can FJX945YTF be used in oscillator circuits?
Yes, the FJX945YTF is explicitly characterized for high-frequency oscillator use, with a 300 MHz current gain bandwidth product (fT) and low output capacitance (Cob = 2.5 pF). Its stable gain and low noise make it suitable for Colpitts, Hartley, and Clapp oscillator topologies operating up to 80 MHz, especially where compact SOT-323 layout is critical.
What does the 'Y' suffix indicate in FJX945YTF?
The 'Y' in FJX945YTF denotes the hFE grade bin: Y-grade devices are tested and guaranteed to exhibit DC current gain between 120 and 240 at VCE = 6 V and IC = 1.0 mA. This replaces generic 'FJX945' part numbers and ensures predictable biasing in production designs without post-manufacture sorting.
FJX945YTF 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:
- 120 @ 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
FJX945YTF FAQ
1.How can I place an order for FJX945YTF through Aetrix?
Please submit a Request for Quotation (RFQ) for FJX945YTF 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 FJX945YTF reliable?
The price and inventory of FJX945YTF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FJX945YTF is usually 5 days.
3.What payment methods are accepted for FJX945YTF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FJX945YTF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FJX945YTF?
FJX945YTF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FJX945YTF 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 FJX945YTF?
For technical support, including FJX945YTF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FJX945YTF requirements.
6.How does Aetrix verify that FJX945YTF is sourced from the original manufacturer or authorized distributors?
All FJX945YTF 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 FJX945YTF meets industry standards.
7.What is the process for return or replacement of FJX945YTF?
All FJX945YTF units undergo pre-shipment inspection (PSI). If there is an issue with FJX945YTF, 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 FJX945YTF part is unused and in its original packaging.
Return procedure for FJX945YTF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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