MOSFETs for RF and broadband comms have higher voltage, power ratings

August 22, 2013 // By Graham Prophet
Microsemi's VRF2944 and VRF3933 high-frequency vertical diffusion metal oxide semiconductor (VDMOS) MOSFET products claim the industry’s highest output power at 50V.

The two higher power, higher voltage devices are designed to operate in the industrial, scientific and medical (ISM) frequency range of 2-60 MHz, in commercial and defence RF power and broadband communications requiring high power and gain without compromising reliability, ruggedness or inter-modulation distortion.

VRF2944 offers 400W or 33% higher output power at 50V supply voltages than competitive devices, including the SD2933, for an increase the power of existing systems by the same 33% or a decrease of cost per W. The gate resistor is integrated on the MOSFET which improves parasitic impedance to maintain the maximum operating frequency at 60MHz. The VRF2944 is capable of operating up to 65V supply voltages where a single VRF2944 can deliver 675W of output power.

VRF3933 is capable of operating up to 100V supply voltages and delivering 300W of output power. The higher voltage MOSFET also gives a higher output impedance, which is easier to match to 50 ohm load. For example, four VRF3933 devices with two in parallel, and those two parallel pairs in push-pull, are capable of launching 1.1 kW with 83V supply voltage through a 4:1 transformer to a 50 ohm load. The devices have nitride passivation for high reliability; and gold metallisation and gold wire bonds for improved reliability; and