NXP Semiconductors BF909,235

Overview

BF909,235 from NXP Semiconductors is an N-channel dual-gate MOSFET in SOT143 package, designed for low-noise RF amplification at 5 V supply with 43 mS typical forward transfer admittance, 3.6–4.3 pF gate-1 input capacitance, and 2.0–2.8 dB noise figure at 800 MHz - deployed in VHF/UHF TV tuners and professional communications receivers.

For engineers reviewing the BF909,235 datasheet, BF909,235 pinout, BF909,235 application, or BF909,235 equivalent, key selection criteria include its dual-gate AGC capability, cross-modulation performance under gain control, thermal resistance (500 K/W), and compatibility with 3–7 V supply systems in high-frequency front-end designs.

Technical Context

The BF909,235 integrates two independent gates (G1 and G2) with source and substrate internally connected, enabling precise AGC via G2 while preserving signal integrity at G1. Its short-channel structure delivers high y_fs/C_ig1-s ratio for optimized gain-bandwidth trade-offs up to 1 GHz.

It operates as a low-noise amplifier with fixed 5 V biasing (V_G2-S = 4 V, V_DS = 5 V, I_D = 15 mA), where G1 controls transconductance and G2 regulates gain dynamically without degrading noise or linearity - validated by 1% cross-modulation voltage curves and scattering parameters up to 1 GHz.

Key Specifications

Pinout & Package

Package: SOT143 - plastic microminiature surface-mount package (2.8 × 1.4 × 0.95 mm), rated for 150 °C junction temperature and optimized for RF layout with minimized lead inductance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-gate MOSFET amplifier applications.

Compared with BF909,235, BF998,215 offers extended bandwidth but demands layout changes, while MRF901LT1G sacrifices AGC simplicity and noise performance for higher power and lower unit cost - making BF909,235 optimal for space-constrained, low-noise, AGC-integrated VHF/UHF amplifiers.

Availability

BF909,235 is available at Aetrix Electronics and suitable for television tuners, professional UHF receivers, FM radio IF stages, and RF test equipment requiring stable component supply with guaranteed long-term sourcing.

Supply support for BF909,235 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 company headquartered in Eindhoven, Netherlands, specializing in high-performance analog, RF, and mixed-signal solutions for consumer, automotive, and industrial markets.

The BF909,235 belongs to NXP's legacy RF transistor product line, engineered specifically for low-noise, dual-gate amplification in VHF/UHF tuner and receiver front-ends with emphasis on AGC linearity and thermal reliability.

FAQ

What is the maximum drain-source voltage rating for BF909,235?

The BF909,235 has a maximum drain-source voltage (V_DS) rating of 7 V, as specified in the Absolute Maximum Ratings table. This allows safe operation across 3–7 V supply rails commonly used in TV tuners and portable UHF receivers. Exceeding this limit risks permanent device failure, and derating is required above 50 °C ambient per the power derating curve in Figure 3.

How does BF909,235 achieve low cross-modulation during AGC operation?

The BF909,235 achieves low cross-modulation through its internal bias circuit and source-substrate interconnection, which stabilizes channel characteristics during gain reduction. At 10 dB gain reduction, typical unwanted voltage remains below 90 dBµV (Fig.4), confirming minimal intermodulation distortion when G2 controls gain - a critical advantage over single-gate alternatives in multi-channel TV reception.

Is BF909,235 pin-compatible with BF909R?

No, BF909,235 and BF909R are not pin-compatible: BF909,235 uses the SOT143 outline (pin 1 = s,b; pin 4 = g1), while BF909R uses SOT143R (pin 1 = s,b; pin 4 = g2 per Fig.2). Their marking codes differ (%M3 vs %M4), and thermal resistance values diverge (500 K/W vs 550 K/W), requiring separate layout and thermal validation for each variant.

What is the typical noise figure of BF909,235 and at what conditions is it measured?

The BF909,235 has a typical noise figure of 2.0 dB at 800 MHz, measured under standardized conditions: T_amb = 25 °C, V_DS = 5 V, V_G2-S = 4 V, I_D = 15 mA, with source and load impedances matched to optimum noise parameters (Γ_opt = 0.603∠67.7°, r_n = 0.581). This value is confirmed in Table 2 and supports high-fidelity signal recovery in sensitive receiver front-ends.

Can BF909,235 operate reliably at 1 GHz?

Yes, BF909,235 maintains usable gain and noise performance up to 1 GHz, as evidenced by s-parameter data (Table 1) and forward transfer admittance plots (Fig.16) showing |y_fs| ≈ 2.3 mS at 1000 MHz. However, gain rolls off above 800 MHz, and system-level matching networks must be optimized per scattering parameters to sustain stability and return loss.