Microsemi 0204-125: A Matched-Input 225–400 MHz RF Power Transistor

The Microsemi 0204-125 is an NPN bipolar RF power transistor built for broadband amplifiers covering 225MHz to 400MHz, the UHF band used heavily by military and aeronautical radios. It is rated for 60V collector-emitter breakdown, 16A collector current and up to 270W dissipation, and is mounted in the chassis-mount 55JT flange package.

Its double input-matched common-emitter design simplifies broadband amplifier layout: part of the input matching is done inside the package, which helps keep gain flat across the band. Typical gain is 7dB to 8.5dB, and the device delivers on the order of 125W output in its intended circuit, as the part number suggests.

Engineers use this class of transistor for final stages of UHF transmitters, jammers and repeaters, and for maintenance of fielded radio systems that were designed around bipolar devices. Replacing them with LDMOS or GaN parts would require new matching networks, bias circuits and requalification, so exact-part sourcing is often cheaper.

Thermal management is the main design challenge. With junction temperatures up to 200°C and hundreds of watts of dissipation, the flange needs a flat, properly torqued mounting surface, good thermal interface material and an adequately rated heat sink. Bias networks must be temperature compensated to avoid thermal runaway in Class AB operation.

Because legacy RF power devices are a common counterfeit target, request original test data and full traceability, and inspect markings and flange finish on receipt.

Detailed parameters, pricing and stock are listed on the 0204-125 Microsemi 60V 225-400MHz NPN RF power transistor page at ChipApex, an independent electronic components distributor in Shenzhen. You can also browse the full catalog at ChipApex.

Microsemi 0204-125: A Matched-Input 225–400 MHz RF Power Transistor

Further reading

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