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NXP Semiconductors BF998R,235
- Part No.:
- BF998R,235
- Manufacturer:
- NXP Semiconductors
- Category:
- Single FETs, MOSFETs
- Package:
- SOT-143R
- Datasheet:
-
BF998R,235.pdf
- Description:
- RF MOSFET 8V SOT143R
- Quantity:
- Payment:
- Shipping:
Inventory:7,513
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Product details
Overview
BF998R,235 from NXP Semiconductors is a silicon N-channel dual-gate MOSFET in SOT143R package, designed for VHF/UHF low-noise amplification with 12 V supply. It delivers 24 mS forward transfer admittance, 2.1 pF gate-1 input capacitance, and 1 dB noise figure at 800 MHz, serving as a gain-controlled RF amplifier in TV tuners and professional communications equipment.
For engineers reviewing the BF998R,235 datasheet, BF998R,235 pinout, BF998R,235 application, or BF998R,235 equivalent, this page provides verified technical context, pin-level circuit roles, real-world RF design implications, and validated alternative options for VHF/UHF front-end amplifier selection.
Technical Context
The BF998R,235 operates as a depletion-mode dual-gate MOSFET with source and substrate internally connected, enabling independent gate biasing for AGC functionality. Its integrated back-to-back gate-source diodes protect against input voltage surges during RF signal handling.
It supports automatic gain control via gate-2 voltage modulation (VAGC), delivering up to −50 dB gain reduction across 0–8 V while maintaining stable 200 mW power dissipation up to 50 °C ambient on ceramic substrate. The device exhibits 25 fF reverse transfer capacitance and 1.05 pF output capacitance at 1 MHz, critical for high-frequency impedance matching.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VDS | 12 V maximum - sets absolute upper limit for drain-source operating voltage in 12 V supply systems. |
| |yfs| | 24 mS typical - defines small-signal transconductance magnitude, directly determining RF gain per unit input drive. |
| Cig1-s | 2.1 pF typical - gate-1 input capacitance governs input impedance matching at VHF/UHF frequencies. |
| F | 1 dB at 800 MHz - quantifies minimum added noise in receiver front-end applications, critical for sensitivity. |
| Ptot | 200 mW maximum at Tamb ≤ 50 °C - constrains thermal design when mounted on PCB or ceramic substrate. |
| V(BR)G1-SS | 6–20 V breakdown range - determines maximum allowable gate-1 reverse bias before conduction or damage. |
| Rth j-a | 500 K/W - junction-to-ambient thermal resistance dictates required heatsinking or layout copper area for reliability. |
Pinout & Package
BF998R,235 uses the SOT143R surface-mount plastic package (SC-61AA), featuring reverse pinning versus SOT143B: Pin 1 = source (s,b), Pin 2 = drain (d), Pin 3 = gate 2 (g2), Pin 4 = gate 1 (g1). Dimensions: 3.0 × 1.4 × 1.1 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (s,b) | Source and substrate connection | Common reference node for both gates and drain; internal tie enables simplified biasing and ESD protection path. |
| 2 (d) | Drain | Main RF output terminal; requires DC blocking and impedance-matching network for optimal power transfer. |
| 3 (g2) | Gate 2 | AGC control input; voltage tuning adjusts transconductance and gain without affecting input match. |
| 4 (g1) | Gate 1 | RF signal input terminal; low 2.1 pF capacitance enables broadband matching into 50 Ω systems. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-gate architecture | Enables independent RF input (g1) and gain control (g2) paths-eliminates need for external AGC diodes or variable attenuators. |
| Integrated back-to-back gate-source diodes | Provides inherent ±5 V input surge protection without adding external clamping components or board space. |
| Low 25 fF Crs | Minimizes Miller effect at UHF frequencies, preserving stability and enabling higher gain without neutralization. |
| 1 dB noise figure @ 800 MHz | Meets stringent sensitivity requirements in digital TV tuners and narrowband professional receivers. |
| −VPG1-S = 2.0 V | Defines gate-1 pinch-off voltage-sets usable gate-1 bias range for linear amplification and AGC headroom. |
Applications
| Television Tuner Front-End | UHF Wireless Microphone Receiver |
|---|---|
|
Use Scenario: Amplifying weak terrestrial broadcast signals (470–862 MHz) prior to mixer stage in analog/digital TV tuner modules. IC Role / Device Role / Timing Role: Low-noise RF amplifier with AGC capability-gate-2 controls gain dynamically as signal strength varies across channel scan. Use Value: 1 dB noise figure preserves SNR in marginal reception areas; 24 mS |yfs| ensures sufficient conversion gain into downstream mixer. |
Use Scenario: First-stage amplification in portable UHF wireless microphone receivers (800–900 MHz band) operating from 12 V battery supply. IC Role / Device Role / Timing Role: High-linearity, low-distortion RF preamplifier with built-in gain control-gate-2 voltage adjusts dynamic range to prevent overload from nearby transmitters. Use Value: 2.1 pF Cig1-s simplifies input matching to antenna; 200 mW Ptot allows robust operation under continuous transmission bursts. |
| Professional Two-Way Radio IF Amplifier | VHF Aircraft Band Receiver Preamp |
|
Use Scenario: Intermediate frequency amplification (210–225 MHz) in land-mobile radio base stations requiring stable gain over temperature and supply variation. IC Role / Device Role / Timing Role: Dual-gate gain-stabilized amplifier-gate-2 biased at fixed voltage to compensate for IDSS drift, maintaining consistent IF gain. Use Value: −VPG2-S = 1.5 V enables precise gate-2 bias setting; 500 K/W Rth j-a supports reliable operation in sealed enclosures without forced air. |
Use Scenario: 118–137 MHz VHF COM band amplification in avionics-grade receivers where EMI immunity and low phase noise are critical. IC Role / Device Role / Timing Role: Low-noise, high-rejection RF amplifier-integrated gate-source diodes suppress transient coupling from adjacent HF/VHF transceivers. Use Value: 25 fF Crs minimizes feedback-induced oscillation risk; SOT143R package allows compact layout with controlled ground return paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-gate MOSFET amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BF998,215 | SOT143B package with standard pinout (g1/g2 swapped vs BF998R,235); identical electrical specs and thermal rating. | Requires PCB layout revision due to reversed gate pin assignment-no direct drop-in replacement. | Select BF998,215 only when redesigning for standard SOT143B footprint or sourcing legacy inventory. |
| MRF901 | Higher 30 mS |yfs
| Better gain but worse noise performance; through-hole mounting limits high-frequency layout integrity. |
Choose MRF901 only if gain priority outweighs noise and miniaturization requirements-unsuitable for dense SMT tuner designs. |
|
Compared with BF998R,235, BF998,215 offers identical RF performance but demands PCB rework for pin compatibility, while MRF901 trades noise and form factor for raw gain-making BF998R,235 the optimal balance for modern SMT-based VHF/UHF low-noise amplifier designs.
Availability
BF998R,235 is available at Aetrix Electronics and suitable for television tuner front-ends, professional UHF wireless receivers, and avionics VHF preamplifiers requiring stable component supply, long-term obsolescence management, and traceable sourcing.
Supply support for BF998R,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
NXP Semiconductors is a global semiconductor leader specializing in high-performance RF, analog, and mixed-signal solutions for automotive, industrial, and consumer applications.
The BF998R,235 belongs to NXP's legacy RF transistor product line, engineered specifically for low-noise, gain-controllable amplification in VHF/UHF broadcast and communications equipment.
FAQ
What is the maximum drain-source voltage rating for BF998R,235?
The BF998R,235 has a maximum drain-source voltage (VDS) rating of 12 V, as specified in the Absolute Maximum Ratings table. This value is not adjustable or derated with temperature-it represents the hard limit beyond which permanent device damage may occur. Operating the BF998R,235 above 12 V violates its safe operating area and voids reliability guarantees.
How does the BF998R,235 achieve automatic gain control (AGC)?
The BF998R,235 achieves AGC by applying a variable DC voltage to gate 2 (g2), which modulates the channel conductivity and thus the forward transfer admittance |yfs|. As shown in Fig.20 of the datasheet, varying VAGC from 0 to 8 V reduces gain by up to 50 dB at 800 MHz. This occurs without altering the input match at gate 1 (g1), preserving system stability and bandwidth.
Is BF998R,235 pin-compatible with BF998,215?
No, BF998R,235 is not pin-compatible with BF998,215. The BF998R,235 uses SOT143R packaging with reverse pinning (Pin 3 = g2, Pin 4 = g1), whereas BF998,215 uses SOT143B (Pin 3 = g1, Pin 4 = g2). Swapping them without PCB modification causes incorrect gate biasing and functional failure. Layout adaptation is mandatory for substitution.
What is the thermal resistance of BF998R,235 and how does it affect PCB layout?
The BF998R,235 has a junction-to-ambient thermal resistance (Rth j-a) of 500 K/W when mounted on a ceramic substrate, per the Thermal Characteristics table. This means a 100 mW power dissipation raises junction temperature by 50 °C above ambient. To maintain Tj ≤ 150 °C, ambient must stay below 100 °C-or PCB copper area must be increased to improve heat spreading beyond the minimal pad footprint.
Does BF998R,235 include ESD protection, and if so, how is it implemented?
Yes, BF998R,235 includes integrated ESD protection via back-to-back diodes between each gate (g1 and g2) and the source (s,b) terminal. This structure clamps transient voltages to approximately ±0.7 V above/below source potential, preventing gate oxide rupture from static discharge. The datasheet explicitly states this protection is "integrated" and forms part of the die design-not an external add-on.
BF998R,235 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- SOT-143R
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Technology:
- MOSFET (Metal Oxide)
- Configuration:
- N-Channel Dual Gate
- Frequency:
- 200MHz
- Gain:
- -
- Voltage - Test:
- 8 V
- Current Rating (Amps):
- 30mA
- Noise Figure:
- 0.6dB
- Current - Test:
- 10 mA
- Power - Output:
- -
- Voltage - Rated:
- 12 V
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-143R
BF998R,235 FAQ
1.How can I place an order for BF998R,235 through Aetrix?
Please submit a Request for Quotation (RFQ) for BF998R,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 BF998R,235 reliable?
The price and inventory of BF998R,235 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BF998R,235 is usually 5 days.
3.What payment methods are accepted for BF998R,235?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BF998R,235 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BF998R,235?
BF998R,235 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BF998R,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 BF998R,235?
For technical support, including BF998R,235 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BF998R,235 requirements.
6.How does Aetrix verify that BF998R,235 is sourced from the original manufacturer or authorized distributors?
All BF998R,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 BF998R,235 meets industry standards.
7.What is the process for return or replacement of BF998R,235?
All BF998R,235 units undergo pre-shipment inspection (PSI). If there is an issue with BF998R,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 BF998R,235 part is unused and in its original packaging.
Return procedure for BF998R,235:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BF998R,235 Tags
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