Analytical study of the photo-effects on common-source and common-drain microwave oscillators using high pinch-off n-GaAs MESFETs

A new analytical study of the photo-effects on common-source and common-drain microwave oscillators using a high pinch-off n-GaAs MESFET has been presented in this paper. The gate-area of the MESFET with a transparent/semitransparent metal at Schottky junction is assumed to be illuminated with optical radiation. The changes in the gate-source and gate-drain capacitances by an induced photovoltage across the Schottky junction due to the incident illumination have been utilized to model analytically the photo-dependent output frequency characteristics of the microwave oscillators. It has been observed from the numerical results that the output frequency of the common-source oscillator is highly influenced by the gate-source capacitance whereas that of the common-drain oscillator is sensitive to the change in the gate-drain capacitance. Further, in both of the oscillators, the output frequencies are decreased with the increase in the intensity level of the incident optical illumination.