Infineon BFR182W NPN RF Transistor: Datasheet, Application Circuit, and Replacement

The Infineon BFR182W is a high-frequency, NPN silicon germanium (SiGe) heterojunction bipolar transistor (HBT) designed primarily for very high-frequency (VHF) to microwave applications. Housed in a compact SOT-343 (SC-70) surface-mount package, this RF transistor is a popular choice for low-noise amplification and oscillation in a wide array of consumer and industrial electronics.

This article provides a detailed overview of its key specifications from the datasheet, a typical application circuit, and potential replacement options.

Datasheet Overview and Key Specifications

The BFR182W is engineered for excellent high-frequency performance. Its SiGe construction offers a superior combination of high transition frequency, low noise, and good linearity compared to standard silicon transistors. Key parameters from the datasheet include:

High Transition Frequency (fT): 12 GHz (typical). This is the frequency at which the transistor's current gain drops to unity, indicating its upper useful frequency limit for amplification.

Low Noise Figure (NF): 1.3 dB (typical at 1 GHz, Ic=5mA). This is a critical parameter for receiver front-ends, as it defines how much noise the transistor adds to the signal. A lower value is always better for sensitive applications.

Collector-Emitter Voltage (VCEO): 12 V. The maximum voltage that can be applied between the collector and emitter terminals.

Collector Current (IC): 30 mA (continuous).

Gain: Offers a high small-signal current gain (hFE) and good power gain at frequencies up to several gigahertz, making it effective for boosting weak signals.

These specifications make the BFR182W exceptionally suited for applications such as:

UHF and VHF amplifier stages

Oscillators and mixer stages in communication systems

Cellular and cordless telephone RF circuits

GPS and satellite receiver front-ends

General-purpose high-frequency switching and amplification

Typical Application Circuit

A common use for the BFR182W is as a low-noise amplifier (LNA) in the first stage of a receiver. The primary goal is to amplify very weak signals from the antenna while adding the minimum amount of noise.

A basic application circuit for a 1 GHz LNA is shown above. Key design elements include:

Biasing: Resistors R1 and R2 form a voltage divider to set a stable DC operating point (quiescent point) on the base. The emitter resistor (Re) provides negative feedback for thermal stability, ensuring stable performance over temperature changes. The collector resistor (Rc) sets the load.

Impedance Matching: For maximum power transfer and optimal noise performance, the input and output must be matched to 50 Ohms. This is achieved using microstrip lines or matching networks with inductors (L1, L2) and capacitors.

Decoupling: Capacitors C1 and C2 are DC blocking capacitors, allowing the RF signal to pass while isolating DC bias levels between stages. Capacitor Ce bypasses the emitter resistor at RF frequencies, maximizing the gain of the transistor.

Replacement and Alternative Options

If the BFR182W is unavailable for a design or project, several factors must be considered when selecting a replacement: package type (SOT-343), key electrical characteristics (fT, Noise Figure, and bias points), and pinout.

Suitable alternative or replacement transistors include:

BFU550X Series (Nexperia): A family of SiGe RF transistors with similar fT and noise performance, available in various packages including SOT-343.

BFR93A (Infineon): A older but very popular RF transistor in a SOT-23 package, though its fT is slightly lower (~6 GHz).

2SC5663 (Toshiba): A high-frequency NPN transistor with comparable specs.

MMBTH10 (onsemi): A general-purpose NPN RF transistor in a SOT-23 package, useful for less demanding applications.

It is crucial to consult and compare the datasheets of any potential replacement to ensure compatibility in the target circuit, especially regarding bias conditions and stability.

ICGOODFIND: The Infineon BFR182W remains a highly reliable and effective solution for low-noise amplification in the VHF to lower microwave spectrum. Its excellent blend of high transition frequency, low noise figure, and small form factor makes it a versatile component in modern RF design. When sourcing a replacement, careful attention to electrical and physical specifications is paramount to maintaining system performance.

Keywords: RF Transistor, Low-Noise Amplifier (LNA), Noise Figure, SOT-343, Silicon Germanium (SiGe)