Rugged, high-voltage RF transistor uses vertical process, yielding better gain
By Paul Rako, Technical Editor -- EDN, April 30, 2008
Start-up HVVi recently introduced the three-member HVVFET (high-voltage-vertical-field-effect-transistor) family of RF-transistor products. Targeting pulsed-radar and avionics applications, the devices employ a process from the company’s investment partner, On Semiconductor. The process employs a vertical structure rather than a lateral structure, providing the devices with better current density and a better thermal path to the heat sink than do LDMOS (laterally diffused metal-oxide-semiconductor) devices. The vertical structure and unique silicon process give the transistors properties rivaling or exceeding those of gallium-nitride and other transistors. The HVVFET's low gate capacitance improves frequency response, its low drain-to-source capacitance improves efficiency, and its low on-resistance improves power handling.
The HVVFET's small footprint, high efficiency, thermal performance, and ruggedness make it appealing in phased-array-radar systems, which can require as many as 1000 RF power devices. Because the HVVFET can withstand a 20-to-1 VSWR (voltage-standing-wave ratio) at rated output power and nominal operating voltage, it requires no heavy circulators and isolators such as those that protect conventional RF transistors. The devices tout at least 15-dB gain, often eliminating the need for gain stages and maintaining the overall signal-path gain. The devices have a 48V power rating, meaning that one power supply can feed both the output and the driver transistors.
All three devices operate at a junction temperature as high as 200°C. The 25V HVV1214-25 has 19-dB gain, operates in the 1.2- to 1.4-GHz range, comes in a 0.2×0.17-in. ceramic surface-mount package, and has a thermal resistance of 1.5°C/W. The 100W HVV1214-100 has 20-dB gain; operates in the 1.2- to 1.4-GHz band; comes in a two-lead, metal-flanged NI-400 package; and has a thermal resistance of 0.8°C/W. The 300W HVV1011-300 has 15-dB gain; operates in the 1.03- to 1.09-GHz band; comes in a two-lead, metal-flanged NI-400 package; and has a thermal resistance of 0.2°C/W. The parts and evaluation kits are available now. HVVi can design parts with custom bandwidth requirements in as little as 90 days. Prices are $135.69, $226.15, and $398.31 (one to 49) for the PVV1214-25, PVV1214-100, and PVV1011-300, respectively.
