Infineon BFR181WH6327XTSA1 RF Transistor Datasheet and Application Notes

The Infineon BFR181WH6327XTSA1 is a high-performance NPN silicon germanium carbon (SiGe:C) RF bipolar junction transistor (BJT) housed in an ultra-miniature SOT-343 (SC-70) surface-mount package. Designed primarily for very high-frequency amplification, this transistor is a cornerstone component in modern RF design, offering an exceptional blend of gain, low noise, and broad bandwidth.

Key Electrical Characteristics and Performance

The BFR181W is engineered to excel in the low-noise amplifier (LNA) and general amplification stages of wireless communication systems. Its standout specifications include a transition frequency (fT) of 8 GHz and a maximum oscillation frequency (fmax) of 12 GHz, making it highly suitable for applications operating in the UHF to S-band frequency ranges (e.g., from several hundred MHz up to approximately 3-4 GHz for optimal performance).

With a low noise figure (NF) of typically 1.1 dB at 900 MHz and 1.6 dB at 1.8 GHz, the device is exceptionally effective at amplifying weak signals while adding minimal intrinsic noise. It provides high gain, with |S21|² measuring around 17 dB at 1 GHz under typical bias conditions (VCE = 5 V, IC = 10 mA). The transistor operates effectively within a collector-emitter voltage (VCE) range up to 15 V and a collector current (IC) up to 30 mA, allowing for flexible biasing to optimize for either maximum gain, linearity, or power efficiency.

Package and Integration

The SOT-343 package is extremely compact, making the BFR181WH6327XTSA1 ideal for space-constrained PCB designs found in smartphones, IoT modules, and other portable wireless devices. The "H" in its part number signifies that it is supplied on tape-and-reel for high-volume, automated assembly processes.

Typical Application Circuits

A common application for the BFR181W is as the first amplification stage in a receiver chain—the LNA. The typical application circuit involves a common-emitter configuration with stable DC biasing, often achieved using a voltage divider network at the base. Proper RF layout is critical; this includes the use of microstrip transmission lines, strategic placement of decoupling capacitors very close to the supply pins to prevent unwanted oscillation, and the implementation of impedance matching networks at both the input and output to ensure maximum power transfer. The datasheet provides S-parameter tables (S11, S12, S21, S22) across various frequencies and bias points, which are essential for designing these matching networks using Smith charts or RF simulation software.

Design Considerations for Stability

A crucial aspect of RF amplifier design is ensuring unconditional stability to prevent oscillations. The BFR181W's datasheet provides parameters to calculate stability factors (e.g., the Rollett stability factor, K). Designers must often use series feedback (e.g., a small emitter inductor) or shunt resistive loading to enhance stability across the entire operating bandwidth, especially when aiming for high gain at lower frequencies.

Conclusion and Summary via ICGOOODFIND

ICGOOODFIND: The Infineon BFR181WH6327XTSA1 is a high-frequency, low-noise RF transistor that is quintessential for amplifying weak signals in wireless applications up to several gigahertz. Its SiGe:C technology provides an excellent balance of performance, integration, and cost-effectiveness. Successful implementation hinges on meticulous attention to RF PCB layout practices, stable biasing, and precise impedance matching to fully leverage its high gain and low noise figure capabilities.

Keywords:

RF Transistor

Low-Noise Amplifier (LNA)

Silicon Germanium Carbon (SiGe:C)

S-Parameters

Impedance Matching