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

Nexperia USA Inc. BF840,235

Name: BF840,235
Brand: Nexperia USA Inc.
SKU: BF840,235
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BF840,235

Manufacturer:: Nexperia USA Inc.

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: BF840,235.pdf

Description:: TRANS NPN 40V 0.025A TO-236AB

Quantity:: RFQ Add To RFQ list

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Inventory:10,000

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Product details

Overview

BF840,235 from Nexperia is an NPN medium-frequency transistor in SOT23 package, rated for V_CEO = 40 V, I_C = 25 mA DC, f_T = 380 MHz, and P_tot = 250 mW at T_amb ≤ 25 °C. It serves as a low-current, low-voltage active device in AM/FM receiver signal paths - specifically in IF amplifiers and AM mixers.

For engineers reviewing the BF840,235 datasheet, BF840,235 pinout, BF840,235 application, or BF840,235 equivalent, key selection criteria include its 380 MHz transition frequency, 67–222 h_FE range at 1 mA/10 V, 0.3 pF feedback capacitance, SOT23 thermal resistance of 500 K/W, and suitability for medium-frequency analog gain stages with tight board space constraints.

Technical Context

This NPN bipolar junction transistor operates in linear active mode for small-signal amplification up to ~300 MHz. Its design emphasizes low noise and stable gain in narrowband RF front-end stages where collector current is held near 1 mA and V_CE is biased at 10 V.

The device uses epitaxial base construction and is optimized for consistent h_FE spread (67–222) and minimal C_re (0.3 pF typ.) to support predictable impedance matching and stability in tuned amplifier configurations without neutralization.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	40 V - Maximum safe collector-emitter voltage under open-base condition; defines upper rail limit for IF stage supply.
I_C (DC)	25 mA - Absolute max continuous collector current; typical operating point is 1 mA for optimal f_T and noise.
f_T	380 MHz - Transition frequency at I_C = 1 mA, V_CE = 10 V; enables stable gain in AM IF (455 kHz) and FM IF (10.7 MHz) bands.
h_FE	67–222 - DC current gain range at I_C = 1 mA, V_CE = 10 V; supports bias design across manufacturing lot variation.
C_re	0.3 pF - Feedback capacitance at V_CB = 10 V, f = 1 MHz; low value reduces risk of oscillation in common-emitter IF amps.
P_tot	250 mW - Total power dissipation on FR4 PCB at 25 °C ambient; sets thermal derating envelope for surface-mount layout.
R_th(j-a)	500 K/W - Junction-to-ambient thermal resistance; requires minimal copper area for thermal management in low-power receivers.

Pinout & Package

SOT23 plastic surface-mounted package (TO-236AB), 3-lead, dimensions per JEDEC MO-203AA: 2.9 × 1.3 × 1.0 mm (L × W × H), with gull-wing leads and standard tape-and-reel packaging (EIA-481-D compliant).

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Control electrode for forward-active bias; requires external resistor network to set I_C ≈ 1 mA in IF amplifier configuration.
2	Emitter	Current sink node; typically grounded via RF choke or AC-coupled to ground through capacitor in tuned amplifier topologies.
3	Collector	Output node; connected to tuned LC tank or IF transformer primary; carries amplified signal with minimal phase shift up to 100 MHz.

Key Features

Feature	Design Value
Medium-frequency optimization	f_T = 380 MHz ensures usable gain margin above 10.7 MHz FM IF while maintaining stability in discrete amplifier designs.
Low feedback capacitance	C_re = 0.3 pF minimizes unwanted coupling from collector to base, reducing need for neutralization in high-gain IF stages.
Controlled h_FE spread	67–222 range allows production-level bias design without individual transistor binning or trim resistors.
SOT23 footprint compatibility	Standard 3-lead SOT23 outline enables drop-in replacement in legacy AM/FM receiver PCBs designed for similar transistors (e.g., BF199, MPSH10).

Applications

AM Mixer Stage

FM IF Amplifier

Use Scenario: Local oscillator (LO) and RF input signals are combined in a passive or active mixer to generate intermediate frequency (IF) output.

IC Role / Device Role / Timing Role: NPN transistor configured as a switching or active mixer core, leveraging nonlinear base-emitter junction for frequency translation.

Use Value: Low V_CEO (40 V) and 380 MHz f_T support reliable mixing at AM band (530–1710 kHz) with minimal intermodulation distortion.

Use Scenario: Amplification of 10.7 MHz IF signal after demodulation in FM radio receivers.

IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier with tuned collector load for selective gain at fixed IF frequency.

Use Value: 0.3 pF C_re and 67–222 h_FE enable stable, predictable gain without neutralization or manual tuning across production units.

AM IF Amplifier

Portable Radio Front-End

Use Scenario: Multi-stage amplification of 455 kHz IF signal in AM broadcast receivers before envelope detection.

IC Role / Device Role / Timing Role: Linear active device biased in forward-active region to deliver broadband voltage gain with low harmonic generation.

Use Value: 250 mW P_tot and 500 K/W R_th(j-a) allow continuous operation on compact FR4 boards without heatsinking.

Use Scenario: Signal conditioning in battery-powered portable radios where size, power efficiency, and EMI resilience are critical.

IC Role / Device Role / Timing Role: Discrete gain element in low-voltage (3–5 V) IF chain, replacing older TO-92 devices to reduce board area.

Use Value: SOT23 package reduces footprint by >70% vs. TO-92; 25 mA I_C max aligns with single-cell alkaline or Li-ion supply constraints.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-frequency transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BF199,115	f_T = 650 MHz, V_CEO = 25 V, h_FE = 40–120, SOT23 package	Higher f_T but lower breakdown voltage; less suitable for 40 V supply rails in AM mixer designs.	Select when higher frequency headroom is needed and supply voltage is ≤25 V.
MPSH10LT1G	f_T = 600 MHz, V_CEO = 25 V, h_FE = 60–120, SOT23 package	Similar f_T, but tighter h_FE spread and lower V_CEO; requires redesign of bias network for 40 V operation.	Prefer for new designs targeting 25 V systems with emphasis on consistency over voltage margin.

Compared with BF199,115 and MPSH10LT1G, BF840,235 offers superior voltage rating (40 V) at the cost of lower f_T, making it uniquely suited for legacy AM receiver designs requiring robustness against supply transients and compatibility with existing 40 V IF stage topologies.

Availability

BF840,235 is available at Aetrix Electronics and suitable for AM/FM receiver design, IF amplifier modules, and portable radio front-end development requiring stable component supply and long-term obsolescence management.

Supply support for BF840,235 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

Nexperia is a global leader in high-volume discrete, logic, and PowerMOS semiconductors, with engineering roots in Philips and NXP Standard Products.

The BF840,235 belongs to Nexperia's legacy RF bipolar transistor portfolio, developed specifically for analog signal processing in consumer broadcast equipment where reliability, consistency, and SMT manufacturability are essential.

FAQ

Is BF840,235 suitable for RF amplifier designs above 100 MHz?

Yes - its 380 MHz f_T and 0.3 pF C_re support stable small-signal amplification up to ~150 MHz in common-emitter configuration. However, gain rolls off above 100 MHz; for >200 MHz applications, BF199 or MMBT5179 offer higher f_T and better high-frequency linearity.

What is the maximum recommended DC bias current for optimal noise figure?

Data sheet characterization shows lowest noise figure at I_C ≈ 0.5–1.0 mA with V_CE = 10 V. Operating above 2 mA increases thermal noise and degrades f_T; staying within 0.5–1.5 mA ensures best trade-off between gain, noise, and stability in IF stages.

Can BF840,235 replace BF240 in existing AM radio PCBs?

No - BF240 is a PNP transistor in TO-92 package with different polarity, pinout, and V_CEO = 30 V. BF840,235 is NPN and SOT23; direct substitution would require schematic revision, layout change, and bias network redesign to accommodate polarity and footprint differences.

Does BF840,235 have qualified automotive-grade variants?

No - BF840,235 is qualified to industrial temperature range (−65 °C to +150 °C) but is not AEC-Q101 qualified. For automotive AM/FM tuner modules, Nexperia's BC847B-Q series or PBSS4041T-Q offer AEC-Q101 compliance with comparable f_T and SOT23 packaging.

BF840,235 Specifications

Product attributes: Attribute value

Manufacturer:: Nexperia USA Inc.

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 25 mA

Voltage - Collector Emitter Breakdown (Max):: 40 V

Vce Saturation (Max) @ Ib, Ic:: -

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 67 @ 1mA, 10V

Power - Max:: 250 mW

Frequency - Transition:: 380MHz

Operating Temperature:: 150°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Surface Mount

Supplier Device Package:: TO-236AB

BF840,235 FAQ

1.How can I place an order for BF840,235 through Aetrix?

Please submit a Request for Quotation (RFQ) for BF840,235 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 BF840,235 reliable?

The price and inventory of BF840,235 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BF840,235 is usually 5 days.

3.What payment methods are accepted for BF840,235?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BF840,235 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BF840,235?

BF840,235 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BF840,235 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 BF840,235?

For technical support, including BF840,235 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BF840,235 requirements.

6.How does Aetrix verify that BF840,235 is sourced from the original manufacturer or authorized distributors?

All BF840,235 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 BF840,235 meets industry standards.

7.What is the process for return or replacement of BF840,235?

All BF840,235 units undergo pre-shipment inspection (PSI). If there is an issue with BF840,235, 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 BF840,235 part is unused and in its original packaging.

Return procedure for BF840,235:

1.Submit a request within 90 days.

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

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