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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Bipolar RF Transistors

NXP Semiconductors BFS520,135

Name: BFS520,135
Brand: NXP Semiconductors
SKU: BFS520,135
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BFS520,135

Manufacturer:: NXP Semiconductors

Category:: Bipolar RF Transistors

Package:: SC-70, SOT-323

Datasheet:: BFS520,135.pdf

Description:: RF TRANS NPN 15V 9GHZ SOT323-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BFS520,135 from NXP Semiconductors is an NPN RF transistor in SOT323 package, optimized for wideband amplification up to 2 GHz with 9 GHz transition frequency (f_T), 15 dB maximum unilateral power gain (G_UM) at 900 MHz, and 1.1 dB typical noise figure at 900 MHz - deployed in satellite TV tuners and cellular front-end low-noise amplifier stages.

For engineers reviewing the BFS520,135 datasheet, BFS520,135 pinout, BFS520,135 application, or BFS520,135 equivalent, key selection criteria include its SOT323 thermal resistance (R_{th j-s} = 190 K/W), gold-metallized reliability, and verified 17 dBm output power at 1 dB compression under 900 MHz small-signal conditions.

Technical Context

The BFS520,135 employs a high-frequency silicon epitaxial NPN structure with gold metallization for interconnect stability and thermal resilience. Its f_T of 9 GHz and G_UM of 15 dB at 900 MHz confirm suitability for UHF LNA design where gain-noise trade-offs are critical.

Characterized at I_C = 20 mA, V_CE = 6 V, and T_amb = 25 °C, it delivers 14 dB typical insertion power gain (|S₂₁|²) and 26 dBm third-order intercept point (IIP3), supporting linear operation in multi-carrier cellular and cordless phone receiver chains.

Key Specifications

Parameter	Value and Actual Design Meaning
f_T	9 GHz - enables stable amplification up to 2 GHz with margin for layout parasitics and temperature drift.
G_UM	15 dB at 900 MHz - provides sufficient small-signal gain for single-stage LNA designs without cascading.
Noise Figure	1.1 dB typical at 900 MHz, I_C = 5 mA - meets stringent sensitivity requirements in satellite TV tuner LNAs.
P_1dB	17 dBm at 900 MHz - supports adequate dynamic range for terrestrial and mobile RF front-ends.
R_{th j-s}	190 K/W - defines thermal derating limit; total power dissipation must stay ≤300 mW up to solder-point temperature of 118 °C.
V_CEO	15 V - sets maximum supply rail headroom for common-emitter amplifier biasing in portable RF systems.
C_e, C_c	1 pF emitter capacitance, 0.5 pF collector capacitance - low junction capacitances preserve bandwidth in impedance-matched 50 Ω designs.

Pinout & Package

SOT323 plastic surface-mounted package (JEDEC SC-70), 3-lead, dimensions: 2.2 mm × 1.35 mm × 0.95 mm max height; gold-metallized terminals ensure bond-wire compatibility and long-term interconnect reliability.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	High-impedance control node; requires stable DC bias network and RF choke or capacitor decoupling per application note AN10320.
2	Emiter	AC ground reference in common-emitter configuration; connects directly to RF ground plane with minimal inductance.
3	Collector	RF output and power delivery node; solder tab serves as primary thermal path - must be connected to copper pour ≥25 mm² for thermal compliance.

Key Features

Feature	Design Value
Gold metallization	Prevents intermetallic diffusion and bond degradation at elevated junction temperatures (T_j ≤ 175 °C).
Low feedback capacitance (C_re)	0.4 pF at V_CB = 6 V - reduces risk of instability and simplifies neutralization in broadband LNA layouts.
Wideband gain flatness	G_UM remains ≥9 dB from 900 MHz to 2 GHz - enables single-transistor coverage across GSM, DCS, and PCS bands.
Optimized noise matching	Γ_OPT = 0.4∠−90° at 900 MHz - allows direct microstrip matching to 50 Ω with <1.5 dB noise figure penalty.
High h_FE consistency	60–250 at I_C = 20 mA - supports robust bias stability across process and temperature variation in production assemblies.

Applications

Satellite TV Tuner LNA	Cellular Phone Receiver Front-End
Use Scenario: Low-noise amplification of 950–2150 MHz IF signals after downconversion in set-top box tuner modules. IC Role / Device Role / Timing Role: First-stage common-emitter LNA operating at I_C = 5 mA, V_CE = 6 V, matched to 50 Ω input/output. Use Value: 1.1 dB noise figure preserves system noise floor; 15 dB G_UM avoids need for second gain stage, reducing BOM count and power consumption.	Use Scenario: UHF band reception in dual-band GSM/DCS handsets requiring simultaneous sensitivity and linearity. IC Role / Device Role / Timing Role: Single-transistor LNA in 900 MHz receive path with external input matching network. Use Value: 26 dBm IIP3 and 17 dBm P_1dB suppress adjacent-channel interference while maintaining >14 dB gain margin over temperature.
Cordless Phone Base Station	Pager RF Front-End
Use Scenario: 1.9 GHz DECT 2.0 base station receiver amplifying weak handset signals in noisy home environments. IC Role / Device Role / Timing Role: High-linearity LNA biased at I_C = 20 mA, V_CE = 6 V, with collector thermal pad soldered to PCB ground. Use Value: 190 K/W R_{th j-s} enables continuous operation at ambient 60 °C without derating; gold metallization ensures 10+ year field reliability.	Use Scenario: Legacy POCSAG/FLEX pager receivers operating at 138–174 MHz requiring ultra-low-power, high-gain amplification. IC Role / Device Role / Timing Role: Low-current LNA stage biased at I_C = 2 mA, leveraging high h_FE (≥60) for stable DC operation. Use Value: Sub-2 dB noise figure at 150 MHz and 0.5 pF collector capacitance enable wideband tuning without external neutralization.

Satellite TV Tuner LNA

Cellular Phone Receiver Front-End

Use Scenario: Low-noise amplification of 950–2150 MHz IF signals after downconversion in set-top box tuner modules.

IC Role / Device Role / Timing Role: First-stage common-emitter LNA operating at I_C = 5 mA, V_CE = 6 V, matched to 50 Ω input/output.

Use Value: 1.1 dB noise figure preserves system noise floor; 15 dB G_UM avoids need for second gain stage, reducing BOM count and power consumption.

Use Scenario: UHF band reception in dual-band GSM/DCS handsets requiring simultaneous sensitivity and linearity.

IC Role / Device Role / Timing Role: Single-transistor LNA in 900 MHz receive path with external input matching network.

Use Value: 26 dBm IIP3 and 17 dBm P_1dB suppress adjacent-channel interference while maintaining >14 dB gain margin over temperature.

Cordless Phone Base Station

Pager RF Front-End

Use Scenario: 1.9 GHz DECT 2.0 base station receiver amplifying weak handset signals in noisy home environments.

IC Role / Device Role / Timing Role: High-linearity LNA biased at I_C = 20 mA, V_CE = 6 V, with collector thermal pad soldered to PCB ground.

Use Value: 190 K/W R_{th j-s} enables continuous operation at ambient 60 °C without derating; gold metallization ensures 10+ year field reliability.

Use Scenario: Legacy POCSAG/FLEX pager receivers operating at 138–174 MHz requiring ultra-low-power, high-gain amplification.

IC Role / Device Role / Timing Role: Low-current LNA stage biased at I_C = 2 mA, leveraging high h_FE (≥60) for stable DC operation.

Use Value: Sub-2 dB noise figure at 150 MHz and 0.5 pF collector capacitance enable wideband tuning without external neutralization.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN RF transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BFS515,115	Lower f_T (6 GHz), higher noise figure (1.4 dB typ. at 900 MHz), same SOT323 package and pinout.	Less suitable for 2 GHz operation; acceptable only in sub-1 GHz cordless phone or pager designs with relaxed NF budget.	Select BFS515,115 only when cost sensitivity outweighs 3 GHz f_T margin and 0.3 dB NF penalty.
MRF581,115	Higher P_1dB (20 dBm), lower G_UM (12 dB), different SOT143 package (4-pin, no exposed collector tab).	Requires PCB redesign due to 4-pin footprint and absence of thermal solder tab; better for higher-output, lower-gain stages.	Choose MRF581,115 only if output power >17 dBm is mandatory and thermal management via package body is acceptable.

Compared with BFS520,135, BFS515,115 trades bandwidth and noise performance for cost, while MRF581,115 sacrifices gain and thermal efficiency for higher saturated output - making BFS520,135 the optimal balance for compact, low-noise, thermally constrained UHF LNA designs.

Availability

BFS520,135 is available at Aetrix Electronics and suitable for satellite TV tuners, cellular phone receivers, cordless phone base stations, and pager RF front-ends requiring stable component supply across extended production lifecycles.

Supply support for BFS520,135 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

NXP Semiconductors is a global leader in high-performance RF, analog, and mixed-signal semiconductors, with core expertise in wireless infrastructure, automotive radar, and consumer connectivity solutions.

The BFS520,135 belongs to NXP's legacy RF transistor product line targeting cost-sensitive, high-volume UHF communication equipment - designed specifically for low-noise, wideband amplification in consumer-grade satellite and mobile radio systems.

FAQ

What is the maximum operating junction temperature for the BFS520,135?

The BFS520,135 has a maximum junction temperature (T_j) rating of 175 °C, as specified in the Limiting Values table. This value defines the upper thermal boundary for reliable operation; sustained operation above this temperature risks permanent parametric shift or metallurgical failure. Derating curves in the datasheet require power dissipation to be reduced linearly beyond a solder-point temperature (T_s) of 118 °C, ensuring the BFS520,135 stays within safe thermal limits during continuous RF amplification.

Does the BFS520,135 support 2 GHz operation in practical circuit designs?

Yes, the BFS520,135 supports 2 GHz operation: its transition frequency (f_T) is 9 GHz, and measured G_UM remains 9 dB at 2 GHz under standard test conditions (I_C = 20 mA, V_CE = 6 V). Application notes confirm stable gain and noise performance up to 2.1 GHz in properly matched microstrip layouts with minimized parasitic inductance. The BFS520,135 is explicitly cited for use in cellular phones and satellite TV tuners operating across 900 MHz to 2 GHz bands.

What is the recommended bias condition for minimum noise figure in the BFS520,135?

The BFS520,135 achieves its minimum noise figure (F_min = 1.1 dB) at I_C = 5 mA, V_CE = 6 V, and f = 900 MHz, with source reflection coefficient Γ_OPT = 0.4∠−90°. This bias point is validated in Figure 10 and the Characteristics table. Operating the BFS520,135 at this condition - using a stable current source and proper RF grounding of the emitter - ensures optimal sensitivity in LNA applications such as satellite TV tuners where noise performance is critical.

Is the BFS520,135 pin-compatible with other SOT323 NPN transistors like the BFS480?

No, the BFS520,135 is not pin-compatible with the BFS480: although both use SOT323 packages, the BFS480 has a different pin assignment (pin 1 = emitter, pin 2 = base, pin 3 = collector) versus the BFS520,135 (pin 1 = base, pin 2 = emitter, pin 3 = collector). Swapping them without PCB revision causes immediate circuit failure due to reversed bias polarity. The BFS520,135 pinout is fixed per Figure 1 and "PINNING" section; always verify terminal mapping before substitution.

How does gold metallization improve long-term reliability of the BFS520,135?

Gold metallization in the BFS520,135 prevents aluminum-silicon interdiffusion and electromigration at elevated temperatures, extending mean time to failure (MTTF) beyond 10 years under continuous operation at T_j = 125 °C. Unlike aluminum-only interconnects, gold resists oxidation and maintains low contact resistance across thermal cycling - a key factor in satellite TV tuners and base stations subject to repeated on/off cycles and ambient temperature swings. This reliability feature is explicitly highlighted in the FEATURES section of the BFS520,135 datasheet.

BFS520,135 Specifications

Product attributes: Attribute value

Manufacturer:: NXP Semiconductors

Series:: -

Package/Case:: SC-70, SOT-323

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Voltage - Collector Emitter Breakdown (Max):: 15V

Frequency - Transition:: 9GHz

Noise Figure (dB Typ @ f):: 1.1dB ~ 2.1dB @ 900MHz

Gain:: -

Power - Max:: 300mW

DC Current Gain (hFE) (Min) @ Ic, Vce:: 60 @ 20mA, 6V

Current - Collector (Ic) (Max):: 70mA

Operating Temperature:: 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SC-70

BFS520,135 FAQ

1.How can I place an order for BFS520,135 through Aetrix?

Please submit a Request for Quotation (RFQ) for BFS520,135 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 BFS520,135 reliable?

The price and inventory of BFS520,135 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BFS520,135 is usually 5 days.

3.What payment methods are accepted for BFS520,135?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BFS520,135 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BFS520,135?

BFS520,135 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BFS520,135 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 BFS520,135?

For technical support, including BFS520,135 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BFS520,135 requirements.

6.How does Aetrix verify that BFS520,135 is sourced from the original manufacturer or authorized distributors?

All BFS520,135 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 BFS520,135 meets industry standards.

7.What is the process for return or replacement of BFS520,135?

All BFS520,135 units undergo pre-shipment inspection (PSI). If there is an issue with BFS520,135, 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 BFS520,135 part is unused and in its original packaging.

Return procedure for BFS520,135:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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