STMicroelectronics SD57045

Overview

SD57045 from STMicroelectronics is a common-source N-channel enhancement-mode lateral MOSFET RF power transistor designed for broadband base station amplifiers operating up to 1.0 GHz. It delivers 45 W output power with 13 dB gain at 945 MHz, 28 V drain supply, and 250 mA quiescent drain current, featuring 1.4 °C/W junction-to-case thermal resistance and ±20 V gate-source voltage rating.

For engineers reviewing the SD57045 datasheet, SD57045 pinout, SD57045 application, or SD57045 equivalent, this device is selected for high-linearity RF power stages in 900 MHz cellular infrastructure where thermal stability, load mismatch tolerance (10:1 VSWR), and broadband gain flatness are critical design requirements.

Technical Context

The SD57045 operates in common-source configuration with lateral MOSFET architecture optimized for RF power amplification. Its 65 V drain-source breakdown voltage and 5 A maximum drain current support robust operation under dynamic load conditions typical of PEP-driven base station transmitters.

Thermal design is enabled by its M243 epoxy-sealed package with direct die-to-case conduction path, achieving 1.4 °C/W R_th(j-c). Impedance data shows Z_IN = 1.04 + j0.71 Ω and Z_DL = 2.30 − j1.52 Ω at 945 MHz, enabling stable matching network design for high-efficiency Class AB operation.

Key Specifications

Pinout & Package

M243 epoxy-sealed package: 3-terminal ceramic/metal hybrid housing with flange for mechanical mounting and thermal interface. Dimensions: 5.72 × 6.48 × 20.57 mm (L × W × H), flange thickness 0.15 mm, lead pitch 9.40 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF454 and PD57045, the SD57045 offers optimal balance of gain, efficiency, and thermal performance in the M243 ceramic package - making it preferred for thermally constrained, high-linearity 900 MHz base station final stages.

Availability

SD57045 is available at Aetrix Electronics and suitable for cellular infrastructure, public safety radio repeaters, and ISM band wireless access points requiring stable component supply, long-lifecycle support, and traceable sourcing for production programs.

Supply support for SD57045 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, Switzerland, specializing in power management, analog, MEMS, and RF solutions for industrial, automotive, and communications markets.

The SD57045 belongs to ST's LdmoST family of lateral RF power MOSFETs, engineered specifically for high-efficiency, high-linearity base station amplifiers operating below 1 GHz - emphasizing thermal robustness and broadband impedance matching.

FAQ

What is the recommended gate bias voltage for linear operation at 45 W POUT?

The SD57045 achieves optimal linearity and efficiency at 45 W POUT with V_GS(Q) = 2.5–5.0 V (typical 3.8 V) at I_DQ = 250 mA and V_DS = 28 V. Bias networks must use low-TC resistors and stable decoupling to maintain quiescent point across temperature; ST recommends using the test fixture's R1/R2 values (18 kΩ and 4.7 MΩ) for initial setup.

Can the SD57045 be operated safely at 32 V drain supply?

No - absolute maximum V(BR)DSS is 65 V, but the device is characterized and qualified only up to 28 V. Operation at 32 V exceeds the specified safe operating area and risks premature failure due to increased electric field stress and reduced SOA margin; ST's application notes explicitly prohibit drain voltages above 28 V for this part.

Is external harmonic filtering required for spectral compliance?

Yes - the SD57045 exhibits significant 2nd and 3rd harmonic content (measured S22 phase shift confirms poor harmonic termination). The 945 MHz test circuit includes C10 (3.0 pF), C8 (6.2 pF), and L1/L2 for fundamental matching and harmonic suppression; omitting these results in >−20 dBc harmonic levels violating FCC Part 22 and ETSI EN 301 908 limits.

What is the maximum allowable case temperature for continuous 45 W operation?

At 45 W POUT and 33–40% efficiency, power dissipation is ~65–70 W. With R_th(j-c) = 1.4 °C/W, junction temperature rise is 91–98°C above case temperature. To stay within T_j(max) = 200°C, maximum case temperature is 102–109°C - however, ST specifies 70°C as the maximum case temperature for rated 93 W P_DISS, so sustained 45 W operation requires active cooling to maintain T_c ≤70°C.