STMicroelectronics LET9045

Overview

LET9045 from STMicroelectronics is a common-source N-channel enhancement-mode lateral MOSFET RF power transistor in PowerSO-10RF package, rated for 80 V drain-source voltage, 9 A continuous drain current, and delivering 45 W output power with 17.5 dB typical gain at 960 MHz under 28 V supply. It features ESD protection (HBM Class 2), 1.2 °C/W junction-to-case thermal resistance, and is optimized for base station amplifiers operating up to 1 GHz.

For engineers reviewing the LET9045 datasheet, LET9045 pinout, LET9045 application, or LET9045 equivalent, key selection criteria include its 960 MHz RF performance at 28 V, thermal stability in plastic SMD packaging, linearity for broadband cellular infrastructure, and compatibility with JEDEC-approved PowerSO-10RF mounting per AN1294.

Technical Context

The LET9045 employs ST's LDMOS technology in a lateral structure, enabling high gain and linearity while maintaining thermal robustness up to 165 °C junction temperature. Its static characteristics include 2.0–5.0 V gate threshold and 1.2 V on-resistance at 3 A, supporting stable biasing at 300 mA quiescent current.

Dynamically, it achieves 65% drain efficiency and withstands 10:1 load VSWR across all phase angles at 960 MHz - critical for ruggedized base station final-stage operation. The device operates exclusively in common-source configuration with gate, source, and drain terminals fully isolated per PowerSO-10RF mechanical layout.

Key Specifications

Pinout & Package

LET9045 is housed in PowerSO-10RF - ST's first JEDEC-approved high-power SMD plastic RF package, available in formed-lead and straight-lead variants. It provides mechanical robustness, RF-optimized leadframe geometry, and compatibility with standard reflow assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF6P21140HR5 and PD85004, LET9045 offers balanced 45 W output, proven thermal behavior in plastic SMD packaging, and simplified biasing - making it optimal for mid-tier 900 MHz infrastructure where reliability, manufacturability, and thermal margin are primary constraints.

Availability

LET9045 is available at Aetrix Electronics and suitable for cellular base station design, public safety radio development, and industrial RF heating systems requiring stable component supply and long-term lifecycle support.

Supply support for LET9045 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 automotive, industrial, and power discrete technologies with vertical manufacturing capabilities.

The LET9045 belongs to ST's LdmoST plastic family of RF power transistors, engineered specifically for broadband commercial and industrial infrastructure applications demanding high gain, linearity, and thermal resilience in surface-mount form.

FAQ

What is the recommended gate bias voltage for LET9045 in Class AB operation?

The LET9045 is specified for 300 mA quiescent drain current (IDQ), achieved with a gate-source voltage (VGS(Q)) between 2.0 V and 5.0 V at VDS = 28 V. Typical design uses 3.5–4.2 V with temperature-compensated bias networks to maintain stable IDQ across –40 °C to +85 °C ambient.

Does LET9045 require an external heatsink when mounted on a standard FR4 PCB?

No external heatsink is required if the PowerSO-10RF thermal pad is soldered to ≥4 cm² of 2-oz copper with ≥6 thermal vias. With RthJC = 1.2 °C/W and max PDISS = 79 W at TC = 70 °C, board-level thermal design alone sustains full 45 W RF output under controlled airflow conditions.

Is LET9045 suitable for pulsed RF applications such as radar transmitters?

No - LET9045 is characterized and qualified for continuous-wave (CW) and modulated broadband signals (e.g., GSM, LTE) up to 1 GHz. Its Safe Operating Area (SOA) and transient thermal response are not validated for high-duty-cycle radar pulses, and no pulse-rated specifications are provided in the datasheet.

Can LET9045 be used with 50 V drain supply instead of the specified 28 V?

No - absolute maximum V(BR)DSS is 80 V, but dynamic performance (gain, efficiency, linearity) is only characterized at 28 V. Operation at 50 V exceeds the validated bias and matching conditions, risks exceeding SOA limits, and voids guaranteed RF specifications per ST's preliminary data disclaimer.