STMicroelectronics ST9045C

Overview

ST9045C from STMicroelectronics is a common-source N-channel enhancement-mode LDMOS RF power transistor designed for broadband base station amplifiers operating up to 1.5 GHz. It delivers 63 W output power at 945 MHz with 18.5 dB gain and 70% drain efficiency under 28 V, 300 mA quiescent bias, and 1 W input drive - optimized for high-linearity cellular infrastructure applications.

For engineers reviewing the ST9045C datasheet, ST9045C pinout, ST9045C application, or ST9045C equivalent, key selection criteria include its 90 V V(BR)DSS rating, 1.0 °C/W junction-to-case thermal resistance, 54 pF Ciss, 9 A continuous drain current capability, and M243 hermetic flanged package suitability for high-power RF PA stages.

Technical Context

The ST9045C employs lateral DMOS structure with gate-controlled channel modulation for stable RF amplification in common-source configuration. Its impedance data (ZIN = 0.76 + j0.11 Ω, ZDL = 5.2 – j0.87 Ω at 945 MHz) enables broadband matching without external harmonic tuning.

Designed for Class AB operation, it supports wide VDD range (20–32 V) and exhibits robust load mismatch tolerance (20:1 VSWR across all phase angles at 45 W POUT), making it suitable for deployed macrocell and distributed antenna systems where impedance variation is inherent.

Key Specifications

Pinout & Package

M243 is a 3-pin, flanged, non-hermetic ceramic/metal package with integrated thermal slug. Dimensions: 14.27 mm × 20.57 mm × 4.45 mm (L × W × H), featuring low-inductance source grounding via metal tab and optimized RF port layout for minimal parasitic coupling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRFE6VP6300H and QPD1025, the ST9045C offers optimal balance of 900 MHz gain-efficiency trade-off, proven reliability in field-deployed macrocells, and direct compatibility with existing 28 V LDMOS-based PA designs - minimizing redesign effort while meeting stringent linearity and thermal targets.

Availability

ST9045C is available at Aetrix Electronics and suitable for macrocell base station PA modules, repeater RF front-ends, and public safety radio infrastructure requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for ST9045C 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 solutions with vertical manufacturing capabilities.

The ST9045C belongs to ST's RF Power LDMOS transistor product line, engineered specifically for high-efficiency, high-linearity cellular infrastructure amplifiers operating below 1.5 GHz - emphasizing thermal robustness, broadband matching, and field-proven reliability.

FAQ

What is the recommended gate bias voltage for linear operation at 945 MHz?

The ST9045C achieves optimal linearity and efficiency at VGS(Q) = 2–5 V with IDQ = 300 mA. For Class AB operation, a fixed gate bias of 3.2 V is typically used, verified by the datasheet's Figure 6 showing stable POUT and I_D vs. V_GS curves at 1 W input drive and 28 V V_DD.

Can ST9045C be operated at 32 V supply without derating?

Yes - the absolute maximum V(BR)DSS is 90 V, and typical performance graphs (Figure 3) confirm stable 60+ W POUT and >65% efficiency at 32 V with IDQ = 300 mA. However, thermal design must accommodate increased P_DISS; junction temperature must remain ≤200 °C using the specified 1.0 °C/W R_thJC.

Is external gate protection required against ESD?

Yes - although the device includes internal ESD protection diodes, ST recommends adding a 10 Ω series gate resistor and 100 pF RF bypass capacitor to ground per the test circuit (Figure 10). This prevents oscillation and limits peak gate current during fast transients, especially in high-humidity or high-static environments.

Does the M243 package require solder paste or conductive epoxy for heatsink attachment?

The M243 flange is designed for mechanical clamping with thermal interface material (TIM), not soldering. ST specifies use of silicone-based thermal grease (e.g., Dow Corning TC-5122) or phase-change pads (e.g., Laird TPCM 600) between the metal tab and heatsink - soldering risks ceramic cracking and void formation due to CTE mismatch.