STMicroelectronics SD1726

Overview

SD1726 from STMicroelectronics is a 50 V, 150 W PEP silicon NPN RF power transistor in common-emitter configuration, optimized for HF SSB communications at 30 MHz with 14 dB gain and −30 dBc IMD. It features gold metallization, emitter ballasting for ruggedness, and M174 epoxy-sealed ceramic package.

For engineers reviewing the SD1726 datasheet, SD1726 pinout, SD1726 application, or SD1726 equivalent, key selection criteria include POUT = 150 W PEP at 30 MHz, VCEO = 55 V, Rth(j-c) = 0.75 °C/W, IMD performance under Class AB bias, and thermal derating above 70 °C case temperature.

Technical Context

The SD1726 operates as a high-power RF amplifier in Class AB mode at 30 MHz, with fixed VCE = 50 V and ICQ = 100 mA bias. Its epitaxial planar structure and emitter ballasting enable stable operation under mismatched load conditions typical in HF SSB transceivers.

It delivers 37% drain efficiency at 150 W PEP output, with GOB = 220 pF at 1 MHz and hFE = 18–43.5 (VCE = 6 V, IC = 1.4 A). The device is not rated for continuous-wave operation beyond its 318 W PDISS limit at TCASE = 25 °C.

Key Specifications

Pinout & Package

M174 is a hermetically sealed ceramic-metal package with flange-mounting, 4-terminal configuration (dual-source), rated for high-reliability RF power applications up to 200 °C junction temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF151G and BLF177, the SD1726 uniquely combines hermetic M174 packaging, −30 dBc IMD at full POUT, and 0.75 °C/W thermal resistance-making it optimal for mission-critical HF SSB systems where reliability under load mismatch and environmental stress is non-negotiable.

Availability

SD1726 is available at Aetrix Electronics and suitable for HF amateur transceivers, marine SSB radios, fixed-station linear amplifiers, and tactical military radios requiring stable component supply across extended production lifecycles.

Supply support for SD1726 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 devices for industrial, automotive, and communications markets.

The SD1726 belongs to ST's THA-series RF power transistor family, engineered specifically for rugged HF linear amplification in SSB voice systems where IMD, thermal stability, and environmental resilience are critical.

FAQ

What is the recommended gate/base bias network for SD1726 in Class AB operation?

A stable Class AB bias uses emitter degeneration resistors (0.22 Ω, 5 W) on both emitter pins, a 10 kΩ potentiometer between base and emitter for quiescent current adjustment, and a 100 nF RF bypass capacitor from base to emitter. Bias must be set to 100 mA ICQ at VCE = 50 V with no RF drive, verified using a calibrated current probe.

Can SD1726 be operated in Class C for CW applications?

No-SD1726 is characterized and qualified only for Class A and Class AB operation. Its emitter ballasting and thermal design target linear SSB modulation; Class C operation risks junction overheating due to uncontrolled peak currents and violates the absolute maximum rating for IC (20 A pulsed).

What is the maximum allowable case temperature for continuous 150 W PEP operation?

At 150 W PEP output, the junction temperature must remain ≤200 °C. With Rth(j-c) = 0.75 °C/W and ηD = 37%, power dissipation is ~255 W. Thus, maximum case temperature is 200 − (255 × 0.75) = 10.75 °C-requiring active cooling or derated output above ambient 25 °C.

Is SD1726 RoHS compliant?

Yes-SD1726 (THA15) manufactured after 2006 complies with RoHS Directive 2011/65/EU. Lead-free assembly is confirmed via STMicroelectronics' material declaration MD-00013287, revision D, dated March 2022.