LDMOS Devices Push 1 kW Pulsed Power

Dec. 11, 2007
These wideband power transistors are designed for use with 50-V power supplies and are suited for high-power pulsed applications through 450 MHz.

Jack Browne
Technical Director

Power amplification is critical to a wide range of applications in industrial, medical, military, and scientific applications at frequencies through 450 MHz. For peak power levels to 1 kW, usually multiple transistors and a power combiner are required. But with recent additions to a line of N-channel enhancement-mode laterally diffused metal-oxide-semiconductor (LDMOS) transistors, Freescale Semiconductor (www.freescale.com) has brought new levels of single-device power amplification to those frequencies. The firm's models MRF6VP21KH and MRF6VP41KH offer pulsed output levels to 1 kW through 450 MHz while model MRF6VP2600H delivers 600 W of continuous-wave (CW) output power through 250 MHz. All three LDMOS devices are designed for use at 50 V.

The new devices are based on the company's sixth-generation, high-voltage (VHV6) 50-V LDMOS technology. These high-power devices are well suited for pulsed applications in broadcast, scientific, medical, and radar systems, including in advanced weather radars, magnetic-resonance-imaging (MRI) medical diagnostic equipment, and high-power industrial lasers. In addition to helping to shank the size of these systems, the new high-power devices can add to reliability by lowering the overall parts count in the poweramplifier sections. They complement earlier members of the company's highpower LDMOS device line, which offered pulsed power levels to 1 kW at frequencies to 130 MHz (see Microwaves & RF, July 2007, p. 104).

Model MRF6VP21KH is designed for use from 10 to 235 MHz, with 1000 W peak pulsed output power for a 100- microsecond pulse-width signal at a 20- percent duty cycle and supply of 50 V and 2 A. The LDMOS transistor provides power gain of 24 dB with drain efficiency of better than 67 percent.

Model MRF6VP41KH (see figure) provides 1 kW peak pulsed output power from 10 to 450 MHz when operating with a 100-microsecond pulse-width signal at a 20-percent duty cycle and 50 V supply. It supplies 20.5 dB power gain with 64-percent efficiency and, like the MRF6VP21KH, features low thermal resistance under pulsed conditions. It is well suited for radar and public-safety communications systems.

The lowest-power member of the power LDMOS transistor trio, model MRF6VP2600H, can be used under both continuous-wave (CW) or pulsed operating conditions. It provides 600 W CW output power at 1-dB compression from 10 to 250 MHz when tested with a typical orthogonal-frequencydivision- multiplex (OFDM) directvideo- broadcast-terrestrial (DVBT) signal. It exhibits 25.8 dB power gain with 29 percent efficiency, and achieves adjacent- channel power ratio (ACPR) of -61 dBc at a 4-MHz offset frequency. The device is well suited for FM broadcast and analog and digital VHF television transmitters.

All three devices feature integrated electrostatic- discharge (ESD) protection. They are capable of handling load mismatches as severe as a 10.0:1 VSWR without damage. The devices are designed in air-cavity packaging and are RoHS compliant.

Freescale Semiconductor, RF Division, 2100 E. Elliot Rd., Tempe, AZ 85284; (800) 521-6274,

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