BLF898U

Overview

The BLF898U is a 900 W LDMOS RF power transistor designed for broadcast Doherty, class AB transmitter, and ISM applications. It operates at VDS = 50 V with an average output power of 180 W per section in a balanced configuration. The device features a drain-source breakdown voltage (V(BR)DSS) of 124 V and a gate-source threshold voltage (VGS(th)) ranging from 1.33 V to 2.33 V. In a class-AB broadband application at 800 MHz, it delivers a typical power gain of 20 dB and a drain efficiency of 32%. The thermal resistance from junction to case is 0.12 K/W, and the maximum junction temperature is 225 °C.

Feature Summary

• Designed for symmetric and asymmetric Doherty operation
• Integrated dual-sided ESD protection
• Excellent ruggedness capable of withstanding high load mismatch
• High power gain and efficiency

Applications

• Broadcast transmitter applications in the UHF band
• Digital broadcasting (DVB-T)
• Industrial, Scientific and Medical (ISM) applications

Procurement Notes

Verify the specific package variant required for the design, as the BLF898U corresponds to the SOT539A flanged balanced ceramic package with mounting holes. Confirm that the ordering suffix matches the exact physical dimensions and lead configuration needed for the PCB layout. Ensure compliance with RoHS directives before finalizing procurement specifications.

Selection Notes

Select the BLF898U for high-power UHF broadcast applications requiring robust performance under varying load conditions. The device supports both symmetric and asymmetric Doherty architectures. Verify that the system can maintain the case temperature within limits to ensure the specified 0.12 K/W thermal resistance is achieved. Consider the 120 V drain-source voltage rating when designing bias networks.

Part Context

The BLF898U belongs to Ampleon's UHF power LDMOS transistor family, specifically engineered for broadcast transmitter applications. It is part of a series that includes variants like the BLF898S, which differs primarily in its earless flanged package design. These transistors are optimized for digital broadcasting standards such as DVB-T, providing high linearity and efficiency in class AB operation.

Replacement Considerations

The BLF898S is a direct functional alternative offering identical electrical characteristics but utilizes the SOT539B earless flanged balanced ceramic package. Designers must verify mechanical compatibility, specifically the absence of mounting holes on the SOT539B variant, before substituting.