STMicroelectronics PD85035C

Overview

PD85035C from STMicroelectronics is a common-source N-channel enhancement-mode LDMOS RF power transistor designed for broadband mobile radio amplification at 945 MHz. It delivers 35 W output power with 14.5 dB gain and 77% drain efficiency at 13.6 V, housed in a BeO-free M243 ceramic package with ESD protection and 200 °C max junction temperature.

For engineers reviewing the PD85035C datasheet, PD85035C pinout, PD85035C application, or PD85035C equivalent, key selection criteria include its 945 MHz P3dB performance, thermal resistance of 1.2 °C/W, gate threshold voltage of 3.9 V, load mismatch tolerance up to 20:1 VSWR, and suitability for car mobile radio final-stage amplifiers requiring high linearity and reliability.

Technical Context

This LDMOS device operates in common-source configuration with fixed 350 mA quiescent drain current, optimized for Class AB linear amplification in the 800–1000 MHz band. Its impedance matching (ZIN = 1.08 + j2.05 Ω at 945 MHz) and low CRSS (1.4 pF) support stable broadband gain and minimal intermodulation distortion.

The transistor uses lateral diffusion architecture enabling high thermal stability and robustness against load mismatch - critical for vehicular RF systems where antenna VSWR varies dynamically. Its 1.2 °C/W RthJC and 200 °C TJ(max) allow sustained 35 W operation without active cooling in compact enclosures.

Key Specifications

Pinout & Package

PD85035C is housed in an epoxy-sealed M243 ceramic package (2-lead, non-hermetic, flanged), measuring 20.57 mm × 14.27 mm × 6.10 mm (L×W×H), with metalized base for direct thermal attachment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF6V2350N and PD57035-E, PD85035C offers optimal balance of 13.6 V operation, 14.5 dB gain, and 1.2 °C/W thermal resistance - making it uniquely suited for space-constrained, battery-powered mobile radio final stages where supply voltage and board area are fixed constraints.

Availability

PD85035C is available at Aetrix Electronics and suitable for car mobile radio transmitters, land mobile radio base stations, industrial UHF telemetry links, and marine VHF amplifier modules requiring stable component supply and long-term lifecycle support.

Supply support for PD85035C 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, designing and manufacturing analog, microcontroller, power, and RF solutions for industrial, automotive, and consumer markets.

PD85035C belongs to ST's LdmoST family of RF power transistors, engineered specifically for high-efficiency, high-linearity broadband amplification in mobile and infrastructure radio systems operating below 1 GHz.

FAQ

What is the recommended gate bias voltage for PD85035C in Class AB operation?

The datasheet specifies VGS(Q) = 3.9 V at IDQ = 350 mA and VDS = 10 V. This is the nominal gate-to-source DC bias required to establish the quiescent drain current. Stable operation demands a low-impedance, well-filtered bias network to prevent oscillation and thermal runaway.

Can PD85035C operate safely with a 17 V supply?

Yes - absolute maximum V(BR)DSS is 40 V, and the datasheet includes load mismatch test data at 17 V. However, POUT and efficiency curves shift; at 17 V and IDQ = 350 mA, P3dB increases to ~50 W but thermal dissipation must be re-evaluated using RthJC = 1.2 °C/W and TJ(max) = 200 °C.

Is external ESD protection required when using PD85035C on PCB?

No - PD85035C integrates on-chip ESD protection rated Class M3 per machine model testing. While this protects against assembly-level handling, system-level I/O pins still require external TVS diodes if exposed to user-accessible connectors or long cables subject to human-body discharge events.

What is the significance of the 20:1 VSWR load mismatch rating?

This rating means the device sustains full 50 W output power (at 17 V) into any complex load impedance corresponding to a 20:1 standing wave ratio - including open, short, and reactive terminations - across all phase angles at 945 MHz. It reflects ruggedness for real-world antenna faults without latch-up or permanent damage.