STMicroelectronics SD1275-01

Overview

SD1275-01 from STMicroelectronics is a 13.6 V, 40 W Class C NPN RF bipolar transistor in M113 plastic package, designed for VHF mobile communications at 160 MHz with 9 dB power gain and emitter-ballasted die for load mismatch tolerance.

For engineers reviewing the SD1275-01 datasheet, SD1275-01 pinout, SD1275-01 application, or SD1275-01 equivalent, key selection criteria include VCEO = 16 V, POUT ≥ 40 W at 160 MHz, thermal resistance Rθ(j-c) = 1.2 °C/W, common-emitter configuration, and ruggedized emitter ballasting for VHF base station and mobile radio final-stage amplification.

Technical Context

This device operates in Class C bias for high-efficiency RF power amplification in VHF band (145–175 MHz), using epitaxial silicon planar construction with emitter ballasting to sustain VSWR > 10:1 without failure. Its static hFE ≥ 20 at IC = 250 mA ensures stable drive-level response in tuned amplifier stages.

The transistor delivers 40 W output with 5 W input at 13.6 V supply and 160 MHz, supported by ZIN = 1.0 + j0.4 Ω and ZCL = 2.3 + j0.1 Ω for optimized matching network design. Dynamic COB = 95 pF limits high-frequency stability margins but remains suitable for fixed-tuned VHF applications.

Key Specifications

Pinout & Package

M113 is a 4-lead plastic epoxy-sealed package with isolated metal tab (collector-connected), intended for surface-mount or through-hole mounting with mechanical heatsink interface. Dimensions: 24.77 mm × 18.42 mm × 4.32 mm (L×W×H), weight ≈ 4.2 g.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar VHF RF power amplifier applications.

Compared with MRF454 and BLW60, SD1275-01 uniquely balances 40 W output, 13.6 V compatibility, built-in emitter ballasting, and cost-effective plastic packaging-making it optimal for production land-mobile and marine radios where reliability under real-world antenna mismatch is essential.

Availability

SD1275-01 is available at Aetrix Electronics and suitable for VHF mobile radio transceivers, land-mobile base stations, amateur radio linear amplifiers, and marine communication systems requiring stable component supply across multi-year production cycles.

Supply support for SD1275-01 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, and RF components for industrial, automotive, and communications markets.

The SD1275-01 belongs to ST's legacy VHF RF power transistor family, engineered specifically for rugged, high-output mobile radio applications where thermal stability and load mismatch resilience are mandatory.

FAQ

What is the recommended bias condition for SD1275-01 in Class C operation?

ST specifies Class C operation with VCE = 13.6 V, IB biased to achieve ICQ ≈ 100–150 mA (quiescent), and RF drive level adjusted to deliver ≥40 W POUT. Base bias must be stabilized with low-inductance resistive divider and bypassed with RF chokes to prevent oscillation.

Can SD1275-01 be used at frequencies outside 145–175 MHz?

Yes, but performance degrades outside this range: gain drops below 7 dB below 145 MHz and thermal instability increases above 175 MHz due to COB = 95 pF limiting fT margin. ST characterizes only 145/160/175 MHz data; operation at 136 MHz or 180 MHz requires full system validation.

Is the metal tab on the M113 package electrically isolated?

No-the metal tab is internally connected to Pin 1 (Collector). It must be mounted to a grounded heatsink with electrically insulating thermal pad or mica washer if chassis ground isolation is required. Direct metal-to-metal contact is mandatory for thermal performance.

Does SD1275-01 require external emitter degeneration resistors?

No-emitter ballasting is integrated into the die geometry, eliminating need for discrete emitter resistors. External degeneration would reduce gain and efficiency; ST's reference designs use direct emitter connection to ground plane via Pins 2 and 4 with minimal trace inductance.