NXP Semiconductors BF1208,115

Overview

BF1208 from NXP Semiconductors is a dual N-channel dual-gate MOSFET IC integrating two low-noise RF amplifiers (Amplifier A and B) with shared source and gate2 terminals, plus an integrated AGC-controlled switch operated by gate1 of Amplifier B. It delivers 31 mS forward transfer admittance (typ), 1.3 dB noise figure at 400 MHz (Amplifier A), and superior cross-modulation performance (105 dBµV at 40 dB AGC). Designed for 5 V VHF/UHF gain-controlled LNA stages in TV tuners and professional comms equipment.

For engineers reviewing the BF1208 datasheet, BF1208 pinout, BF1208 application, or BF1208 equivalent, this page provides verified circuit role, validated SOT666 package mapping, confirmed dual-amplifier dynamic specs (yfs, NF, Xmod), AGC-switch interaction logic, and two field-validated alternative parts for VHF/UHF LNA replacement scenarios.

Technical Context

The BF1208 implements two independent common-source dual-gate MOSFETs sharing physical source and gate2 connections, enabling compact VHF/UHF front-end designs. Amplifier A features fully integrated bias; Amplifier B uses partly integrated bias with gate1 (B) controlling an internal switch that disables Amplifier A when active.

DC stabilization is achieved via on-chip bias circuits, while integrated gate-source diodes protect against ESD and input voltage surges. The device operates with 5 V supply, supports Automatic Gain Control via gate1 voltage modulation, and maintains stable cross-modulation performance across 40 dB AGC range.

Key Specifications

Pinout & Package

The BF1208 is housed in a SOT666 micro-miniature plastic surface-mount package (6-pin, 1.7 × 1.5 mm footprint, 0.5 mm pitch), optimized for high-frequency layout with minimal parasitic inductance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-gate MOSFET LNA applications.

Compared with BF1108,115 and BF998,115, the BF1208 uniquely integrates two amplifiers and an AGC-controlled switch in one SOT666 package-enabling dual-path selection, reduced component count, and guaranteed cross-modulation performance without external switching complexity.

Availability

BF1208 is available at Aetrix Electronics and suitable for digital television tuners, professional UHF radio receivers, and analog TV upgrade modules requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for BF1208 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and consumer applications.

The BF1208 belongs to NXP's RF transistor portfolio designed specifically for high-performance, low-noise VHF/UHF amplification in broadcast and professional communication systems with stringent AGC and linearity requirements.

FAQ

What is the primary function of the integrated switch in the BF1208?

The integrated switch in the BF1208 is controlled by gate1 of Amplifier B and physically disables Amplifier A when activated. This enables automatic selection between the two amplifiers without external components - a key feature for AGC-driven dual-path receiver architectures. The switch behavior is confirmed in Figure 3 and Section 1.1 of the BF1208 datasheet.

Can the BF1208 operate with a 3.3 V supply instead of 5 V?

No - the BF1208 is specified for 5 V operation only. Its limiting values (Table 5) define V_DS max = 6 V and ID max = 30 mA under 5 V conditions; static characteristics (Table 7) and dynamic data (Tables 8 & 11) are all measured at V_DS = 5 V. Operation below 4.5 V degrades noise figure, gain, and cross-modulation performance outside guaranteed specifications.

How does the shared gate2 connection affect RF matching for Amplifier A and Amplifier B?

The shared gate2 terminal requires identical DC bias (4 V typical) and AC grounding for both amplifiers, meaning a single gate2 matching network serves both paths. This simplifies layout but mandates careful isolation of drain outputs (pins 4 and 6) to prevent inter-amplifier coupling. Matching networks must be designed independently for each drain to maintain specified S-parameters (Tables 9 and 12).

What is the maximum allowable junction temperature for continuous operation of the BF1208?

The BF1208 has a maximum junction temperature (T_j) of 150 °C, as specified in Tables 1 and 5. Thermal resistance from junction to solder point (R_th(j-sp)) is 225 K/W (Table 6), so sustained operation near T_j max requires strict control of solder-point temperature (T_sp ≤ 109 °C per Table 5) via adequate PCB copper area and thermal vias.

Is the BF1208 pin-compatible with other NXP dual-gate MOSFETs like the BF998?

No - the BF1208 uses the SOT666 package with a unique 6-pin arrangement (gate1-A, gate2, gate1-B, drain-B, source, drain-A), while the BF998 uses SOT23-6 with different pin assignment (drain, source, gate1, gate2, case, NC). Pinouts are incompatible; PCB layout redesign and schematic updates are required for substitution.