Infineon BF998RE6327: Datasheet, Application Circuit, and Replacement Guide
The Infineon BF998RE6327 is a high-performance, N-channel dual-gate MOSFET designed for very high-frequency (VHF) applications. This component is a staple in RF (radio frequency) circuits, prized for its ability to provide high gain, excellent cross-modulation characteristics, and low noise figure. Its primary function is to amplify weak signals in receivers, making it a critical part of tuners, FM radios, television receivers, and other communication equipment.
Datasheet Overview and Key Specifications
Understanding the BF998RE6327 datasheet is crucial for effective implementation. This surface-mount device (SMD) comes in a SOT-143 package. Its dual-gate structure allows for separate control of gain and mixing, offering superior performance over single-gate transistors. Key absolute maximum ratings and electrical characteristics include:
Drain-Source Voltage (VDS): 12 V
Gate-Source Voltage (VGS): ±8 V
Drain Current (ID): 30 mA
Total Power Dissipation (Ptot): 200 mW
Forward Transfer Admittance (|Yfs|): 30 mS (typical at VDS=10V, f=1MHz)
Capacitance (Gate 1 to Source, Ciss): 1.8 pF (typical)
Noise Figure (NF): Very low, typically around 1.5 dB at 100 MHz, making it exceptionally suitable for sensitive receiver front-ends.
Typical Application Circuit
A common application for the BF998RE6327 is as an RF amplifier in the first stage of a superheterodyne receiver. Its high gain and low noise are essential for amplifying faint antenna signals without significantly degrading the signal-to-noise ratio.
A basic application circuit involves biasing both gates. Gate 1 (G1) is the signal input, typically connected to the tuned input circuit from the antenna. Gate 2 (G2) is used for gain control and automatic gain control (AGC) applications; a variable DC voltage applied here modulates the gain of the device. The drain (D) is connected to the output load, often a tuned transformer or LC circuit, which couples the amplified signal to the next stage (e.g., a mixer). The source (S) is connected to ground, usually through a resistor to set the DC operating point, often bypassed with a capacitor to prevent negative feedback at the operating frequency.
Replacement Guide and Cross-Reference
While the BF998RE6327 remains available, finding alternatives is sometimes necessary due to supply chain issues or design updates. Several transistors offer similar functionality and can serve as potential replacements, though careful cross-referencing of specifications is mandatory.
BF998W: A variant in a different package (SOT-323). Electrical characteristics are nearly identical.
BF990A / BF991: These are also dual-gate MOSFETs from Infineon (formerly Siemens/Epcos) with similar characteristics and are often listed as direct equivalents.
3SK Series (e.g., 3SK131, 3SK222): Japanese equivalents from manufacturers like Toshiba or Hitachi. Their pinouts and electrical parameters are very close, but the datasheet must be checked for any minor differences in capacitance or voltage ratings.
MPF 6601: A JFET alternative that can sometimes be used in less demanding applications, though it may not match the gain or noise performance.
When seeking a replacement, the most critical parameters to match are the maximum voltage ratings, the pinout configuration, the forward transfer admittance (Yfs), and the inter-electrode capacitances. A mismatch in capacitance can detune sensitive RF circuits, leading to a loss of gain or unexpected oscillations.
ICGOODFIND provides comprehensive electronic component information, cross-reference guides, and sourcing data, making it an invaluable resource for engineers seeking details on parts like the BF998RE6327 and its alternatives.
Keywords:
1. Dual-Gate MOSFET
2. RF Amplifier
3. Low Noise Figure
4. Cross-Reference
5. VHF Applications
