SD1274 VHF RF Power Bipolar Transistor Datasheet Summary

1. General Overview

The SD1274 is a Class C epitaxial silicon NPN planar RF power transistor manufactured by STMicroelectronics, specifically designed for VHF (Very High Frequency) mobile communication applications. Operating primarily at 160 MHz with a 13.6 V supply voltage, it delivers a minimum output power of 30 W and a power gain of 10 dB in common-emitter configuration. Key design features include an emitter ballasted die geometry, which enhances robustness against severe load mismatch conditions—critical for reliable performance in mobile communication systems. The transistor is packaged in an epoxy-sealed M135 4-lead stud package, optimized for thermal management and easy mounting. Note that the SD1274 is marked as an obsolete product, with the latest datasheet revision (Revision 2) issued in May 2004.

2. Key Specifications

2.1 Absolute Maximum Ratings (Tcase = 25°C)

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2.2 Electrical Characteristics (Tcase = 25°C)

Static Characteristics

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Dynamic Characteristics

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2.3 Impedance Characteristics

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2.4 Thermal Characteristics

• Thermal Resistance (Junction-to-Case): Inferred from series data for M135 package (typical for 70 W power dissipation: ~2.86 °C/W)
• Package Thermal Design: Stud mounting enables efficient heat transfer to heatsinks, critical for high-power RF operation.

3. Package & Mechanical Details

3.1 Package Specifications

• Package Type: M135 4-lead stud package (epoxy-sealed)
• Pin Configuration (Top View):
• Mounting Feature: #8-32 UNC-2A stud for secure heatsink attachment
• Marking: "SD1274" on package
• Packaging: Black cardboards (per order code specifications)

3.2 Mechanical Dimensions (M135 Package)

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4. Functional Features

4.1 Core Capabilities

• High Power Output: Delivers minimum 30 W output power at 160 MHz, suitable for VHF transmitters in mobile communication systems.
• Robust Load Mismatch Tolerance: Emitter ballasted die design withstands extreme load mismatch, reducing failure risk in dynamic communication environments.
• Efficient Power Gain: 10 dB minimum power gain minimizes drive power requirements, optimizing system efficiency.
• Dual Base Leads: Symmetric base connections enhance current distribution and thermal stability.
• Class C Operation: Optimized for RF amplification in transmitters, balancing efficiency and linearity for communication signals.

4.2 Typical Performance Characteristics

• Power Output vs. Supply Voltage: At 136 MHz, 150 MHz, and 175 MHz, output power increases with supply voltage (10–14 V), with higher input power (1.0–2.0 W) yielding higher output.
• Power Gain vs. Frequency: Maintains stable gain (~10–12 dB) across the VHF band (150–180 MHz), ensuring consistent performance across operating frequencies.
• Power Output vs. Input Power: Linear relationship at rated conditions, with 3.0 W input delivering full 30 W output.

5. Application Information

5.1 Target Applications

• VHF mobile communication transmitters
• Two-way radios and walkie-talkies
• VHF broadcast transmitters (low-power)
• Industrial remote control systems
• Mobile radio base stations (low-power segments)

5.2 Operating Conditions

• Recommended Supply Voltage: 13.6 VDC (optimized for performance)
• Operating Frequency Range: 150–180 MHz (peak performance at 160 MHz)
• Biasing Configuration: Class C common-emitter (requires appropriate base drive circuitry)
• Thermal Management: Must be mounted to a heatsink to maintain case temperature within safe limits (max T_J = 200°C)

6. Ordering & Compliance

• Part Number: SD1274
• Package Type: M135 4-lead stud (epoxy-sealed)
• Marking: SD1274
• Packaging: Black cardboards
• Obsolete Status: Marked as obsolete by STMicroelectronics; replacement parts may be required for new designs.
• Datasheet Revision: Revision 2 (May 2004, no content changes—only stylesheet update from original June 1993 issue)
• Compliance: Not specified (datasheet predates modern RoHS full compliance; consult STMicroelectronics for legacy product compliance details)

7. Safety & Usage Notes

• Critical Applications: Not authorized for use in life support devices or systems without express written approval from STMicroelectronics.
• Absolute Ratings: Exceeding maximum ratings (even momentarily) may cause permanent device damage or reduced reliability.
• Mounting: Ensure proper stud torque and heatsink contact to maximize thermal dissipation and prevent overheating.
• Obsolete Product: Availability may be limited; refer to STMicroelectronics’ product discontinuance notice for recommended replacements.