Infineon BFR182 NPN RF Transistor: Datasheet, Application Circuits, and Replacement Guide

The Infineon BFR182 is a high-frequency NPN bipolar junction transistor (BJT) engineered for very high-frequency (VHF) applications. Housed in a compact SOT-23 surface-mount package, this RF transistor is a common choice for low-power amplifiers, oscillators, and mixer stages in consumer and industrial electronics, such as FM radio, television tuners, and wireless communication modules.

This article provides a detailed overview of its key specifications, typical application circuits, and potential replacements.

Datasheet Overview and Key Specifications

The BFR182 is characterized by its excellent high-frequency performance. Key parameters from its datasheet include:

High Transition Frequency (fT): This is a critical figure of merit for RF transistors. The BFR182 boasts an fT of 8 GHz minimum, indicating its ability to amplify signals effectively into the gigahertz range.

Collector-Emitter Voltage (VCEO): 20 V. This defines the maximum voltage that can be applied between the collector and emitter terminals.

Collector Current (IC): 35 mA. The maximum continuous current the collector can handle.

Noise Figure: Typically around 2 dB at 1 GHz. A low noise figure is essential for the first stage of a receiver (low-noise amplifier or LNA) to ensure weak signals are amplified with minimal added noise.

Gain: It offers a power gain (Gum) of ~16 dB at 1 GHz, making it suitable for providing significant signal amplification.

Package: SOT-23. This small, surface-mount package is ideal for compact PCB designs but requires careful handling during soldering.

Typical Application Circuits

The BFR182 is predominantly used in small-signal amplification stages. Its high fT makes it stable and effective in VHF and UHF circuits.

1. Common-Emitter Amplifier:

The most standard configuration is the common-emitter amplifier. It provides high voltage and power gain. Proper biasing using a voltage divider network on the base is crucial for stable operation. Input and output matching networks, consisting of capacitors and inductors, are used to ensure maximum power transfer at the desired operating frequency, minimizing signal reflection.

2. Low-Noise Amplifier (LNA):

Due to its low noise figure, the BFR182 is an excellent candidate for the first stage of a receiver chain. Designing an LNA requires meticulous PCB layout, impedance matching for noise figure (rather than maximum power), and stable bias points to achieve optimal sensitivity for receiving weak signals.

3. Local Oscillator:

The transistor can be used in oscillator circuits, such as Colpitts or Clapp configurations, to generate a stable high-frequency reference signal required in radio receivers and transmitters.

BFR182 Replacement Guide

Finding a direct replacement for an obsolete or unavailable component is a common task. Several factors must be considered when substituting the BFR182:

Key Parameters to Match: The most critical specifications are transition frequency (fT), noise figure, package (SOT-23), and pinout. The replacement's absolute maximum ratings (VCEO, IC) must meet or exceed the original.

Potential Replacements:

Infineon BFR93A: A very close alternative from the same manufacturer with similar fT (6 GHz) and package.

NXP (formerly Philips) BFG67 / BFG197: These are also general-purpose RF transistors in SOT-23 packages with high fT.

ON Semiconductor MMBTH10: A widely available NPN RF transistor with an fT of 650 MHz, suitable for lower-frequency applications within the BFR182's range.

ROHM 2SC2712: Another SOT-23 packaged RF transistor with comparable characteristics.

Important Note: Always cross-reference the datasheets of the original and the potential replacement thoroughly. Pay close attention to the pinout (E-B-C vs. E-C-B), as it can vary between manufacturers and even between different transistors from the same manufacturer. Slight adjustments to the biasing or matching networks may be required for optimal performance with a substitute part.

ICGOOODFIND: The Infineon BFR182 remains a robust and effective solution for VHF signal amplification and oscillation. Its high transition frequency and low noise figure make it a versatile component in RF design. When sourcing, carefully verify its key specs against your circuit requirements, and use the listed alternatives as a starting point for finding a suitable replacement, ensuring you check for critical pinout compatibility.

Keywords: RF Transistor, VHF Amplifier, SOT-23 Package, Noise Figure, Transition Frequency (fT)