Infineon BFR183E6327HTSA1 RF Transistor: Key Specifications and Application Circuit Design

The Infineon BFR183E6327HTSA1 is a high-performance NPN silicon germanium (SiGe) heterojunction bipolar transistor (HBT) designed for very high-frequency, low-noise amplification. Packaged in the ultra-miniature SOT-343 (SC-70), it is an ideal solution for space-constrained applications in the microwave frequency range, making it a cornerstone component in modern RF design.

Key Specifications

The BFR183E6327HTSA1 excels in its core electrical characteristics, which define its application space:

Transition Frequency (fT): This is a critical metric, indicating the frequency at which the transistor's current gain drops to unity. The BFR183E6327HTSA1 boasts a remarkably high fT of 8 GHz, enabling excellent performance in RF amplification stages operating well into the GHz range.

Noise Figure (NF): A vital parameter for receiver front-ends, the low noise figure of 1.4 dB (typical at 1.8 GHz, VCE=2V, IC=5mA) ensures minimal degradation of the desired signal, preserving signal integrity and reception sensitivity.

Gain: The device provides high gain, with a |S21|² of 16 dB (typical at 1.8 GHz), which is essential for effectively boosting weak signals from an antenna.

Collector-Emitter Voltage (VCEO): Rated at 6 V, it provides sufficient headroom for various low-voltage circuit configurations.

Collector Current (IC): A maximum continuous collector current of 35 mA allows for handling moderate signal power levels.

These specifications collectively position this transistor as a premier choice for low-noise amplifiers (LNAs), driver amplifiers, and oscillator circuits in wireless communication systems.

Application Circuit Design: A 2.4 GHz Low-Noise Amplifier (LNA)

Designing a stable and efficient LNA requires careful attention to biasing, impedance matching, and stability. Below is a guide to a fundamental single-stage LNA design for the 2.4 GHz ISM band (e.g., Wi-Fi, Bluetooth) using the BFR183E6327HTSA1.

1. DC Biasing:

A stable DC operating point (quiescent point) is crucial. A common-emitter configuration with voltage divider bias is often used. The goal is to set a collector current (IC) of ~5 mA and a collector-emitter voltage (VCE) of ~2 V, a sweet spot for optimal noise and gain performance as per the datasheet. Emitter degeneration (a resistor from emitter to ground) is added to improve linearity and stabilize the DC operating point against temperature variations.

2. RF Stability:

Preventing oscillations is paramount. This involves:

Base Stopping Resistor: A small resistor (e.g., 10-100 Ω) in series with the base can significantly dampen potential high-frequency oscillations without greatly affecting RF performance.

Collector RF Choke: An inductor (RFC) is used in the collector bias path to present a high impedance to RF signals, preventing them from leaking into the power supply.

Stability Analysis: The Rollett stability factor (K-factor) must be calculated using S-parameters from the datasheet. If K<1, the circuit is potentially unstable, and corrective matching or feedback networks are required.

3. Impedance Matching:

Maximum power transfer and optimal noise performance are achieved by matching the transistor's impedances to the source (50 Ω) and load (50 Ω).

Input Matching Network: For an LNA, the input is matched for the minimum noise figure (NFmin), not necessarily maximum gain. This is known as a low-noise match. A simple LC network (series inductor, shunt capacitor) is typically used to transform the 50 Ω source impedance to the complex impedance presented by the transistor base for best noise performance.

Output Matching Network: The output is matched for maximum gain to the 50 Ω load. Another LC network transforms the 50 Ω load to the complex conjugate of the transistor's output impedance.

4. Layout and Bypassing:

RF Bypassing: Excellent power supply decoupling is non-negotiable. Use a combination of capacitors (e.g., 100 pF and 0.1 µF) very close to the transistor's collector supply pin to provide a low-impedance path to ground for RF signals.

PCB Layout: Keep all RF trace lengths as short as possible. Use a continuous ground plane on the bottom layer to minimize parasitic inductance and ensure a stable reference plane.

A simulated or measured result of this circuit should show a gain of over 15 dB and a noise figure very close to the transistor's specified NFmin at the target frequency of 2.4 GHz.

ICGOOODFIND

The Infineon BFR183E6327HTSA1 is an exceptional RF transistor that combines high-frequency capability, low-noise performance, and a miniature form-factor. Its well-balanced specifications make it a versatile and reliable building block for designing high-performance amplifier stages in a wide array of wireless applications, from consumer IoT devices to specialized communication equipment. Proper circuit design, focusing on stable biasing and precise impedance matching, is key to unlocking its full potential.

Keywords: Low-Noise Amplifier (LNA), Silicon Germanium (SiGe), RF Transistor, S-Parameters, Impedance Matching.