BF1105R,215

Overview

The BF1105R is an N-channel dual-gate MOS-FET encapsulated in the SOT143R plastic package. It features a short channel transistor with high forward transfer admittance to input capacitance ratio, enabling low noise gain controlled amplifier operation up to 1 GHz. The device includes an internal self-biasing circuit for cross-modulation performance and DC stabilization. Key electrical parameters include a drain-source voltage of 7 V, drain current of 30 mA, total power dissipation of 200 mW at Tamb ≤ 80 °C, and forward transfer admittance of 25–31 mS. Input capacitance at gate 1 is 2.2–2.7 pF, reverse transfer capacitance is 25–40 fF, and noise figure is 1.7–2.5 dB at 800 MHz.

Feature Summary

• Dual-gate architecture with integrated self-biasing circuitry for stable DC operation and improved cross-modulation performance during automatic gain control.
• Internal diodes between gates and source provide protection against excessive input voltage surges.
• Optimized short channel design delivers high forward transfer admittance relative to input capacitance for efficient RF amplification.

Applications

• VHF and UHF television tuners
• Professional communications equipment

Procurement Notes

Verify the specific ordering suffix matches the required package variant, as the BF1105R designation corresponds to the SOT143R outline. Confirm that the component status aligns with current production requirements, noting that datasheet information may be superseded by newer releases. Ensure compliance with RoHS directives and verify anti-static handling protocols are maintained during transport and assembly to prevent electrostatic discharge damage.

Selection Notes

Select this component for applications requiring low noise amplification in the VHF and UHF bands with a 5 V supply. The dual-gate configuration allows independent control of gain and bias, suitable for AGC circuits. Consider the SOT143R package dimensions and thermal resistance characteristics for PCB layout. Verify that the operating junction temperature limits and power dissipation constraints fit within the system's thermal management capabilities.

Part Context

The BF1105R belongs to the BF1105 family of N-channel dual-gate MOS-FETs from NXP Semiconductors. This series is designed for RF applications where low noise and high linearity are critical. The family includes variants with different packaging options, such as the BF1105 in SOT143B and the BF1105WR in SOT343R, allowing designers to choose based on space and thermal requirements while maintaining consistent electrical performance.

Replacement Considerations

Direct substitutes include the BF1105 (SOT143B package) and BF1105WR (SOT343R package). These parts share identical electrical specifications but differ in physical footprint and pinout orientation. Verify package compatibility and pin mapping before substitution to ensure proper integration into existing designs without modifying the PCB layout.

FAQ

What is the function of the second gate in the BF1105R?

The second gate serves as the control input for automatic gain control (AGC), allowing the device to adjust its gain dynamically while maintaining good cross-modulation performance and DC stability through the internal self-biasing circuit.

How does the BF1105R protect against input voltage surges?

The device incorporates integrated diodes between the gates and the source terminal. These diodes clamp excessive input voltages, protecting the internal structure from damage during surge conditions.

What is the maximum operating junction temperature for the BF1105R?

The maximum operating junction temperature (Tj) for the BF1105R is +150 °C, as specified in the limiting values section of the product specification.