High Voltage (50V) LDMOS Devices Provide Excellent Efficiency, Linearity and Gain

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Since the late 1980s, high voltage (50V) VDMOS has been the RF power transistor technology of choice. Recently, though, after years of development, new LDMOS (Laterally Diffused Metal Oxide Semiconductor) processes are delivering similar supply voltages. NXP Semiconductors, building on its mature, sixth-generation (Gen6) LDMOS process, has introduced a new high voltage (HV) LDMOS technology that supports 50V applications in the broadcast, ISM and defense markets.

The new HV LDMOS technology offers superior reliability characteristics, along with NXP’s widely recognized characteristics for ruggedness and mismatch capabilities. The 50V portfolio features high gain, excellent efficiency and very high linearity. As a result, the new devices have substantially reduced thermal resistance, so it’s easier to maintain low junction temperature and high power density and impedance matching is simpler.

NXP’s high voltage (50V) LDMOS portfolio includes the following RF VHF power transistor devices:

 

APPLICATIONS Broadcast ISM Defense market

 

600W, 88 to 108MHz FM Broadcast Application

Figure 2 shows the NXP BLF574 in an FM broadcast application (88 to 108MHz). The push-pull amplifier uses a balun and 4:1 transformers at the input and output. When operated in Class-C with a continuous wave signal, the amplifier delivers a P_1dB of 600W over the entire 88-108MHz frequency band at V_DS=50V. The power gain at the P_1dB point is 28dB with a typical drain efficiency of 74% across the entire 88-108MHz frequency band. At a heatsink temperature of 60°C, the transistor will operate at a comfortable 157°C junction temperature, ensuring excellent reliability. The compact amplifier design is four inches long and doesn’t exceed the width of the transistor, thus enabling small, high power solid-state broadcast amplifier designs. The PC board includes all the RF impedance matching as well as the temperature compensated gate bias circuit.

 

 

 

 Featured Products

Part Number		Description	Data Sheet	App. Notes
BLC573		General Purpose <500MHz, 50V LDMOS, Drain Efficiency 70
BLF571		General Purpose 225MHz VHF Transmitter, 50V LDMOS, Drain Efficiency 70
BLF574		High Voltage (400W), High Power Continuous Wave Device, Power Gain 26dB, Drain Efficiency 70

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