The RF Pulse Susceptibility of UHF Transistors

The electromagnetic susceptibility of UHF transistors is investigated. The 2N5179 RF amplifier type transistor was selected as a representative UHF transistor because of its chip structure. It is a silicon n-p-n epitaxial planar transistor with an interdigitated baseemitter metallization pattern. Several manufacturer's versions were tested. A single RF pulse at 240 MHz was applied directly to the base terminal with the emitter terminal grounded. The incident RF pulse power required to cause a 50 percent failure rate is in the 35-70 W range for a 3 μs pulse duration and in the 150-450 W range for a 0.3 , μs pulse duration. The primary variable is the percentage of the incident power absorbed by the transistor. The absorbed pulse energy required to cause a 50 percent failure rate is in the 20-35 μJoule range for 0.3-3.0, μs pulse durations. The gs pulse and CW RF burnout powers for 2N5179 transistors are similar to those for 1N23 mixer diodes. The data suggest that UHF receivers with an RF transistor amplifier front end may be as susceptible to intense EMR at UHF frequencies as are UHF receivers with a mixer diode front end.