A ring oscillator based on HIFETs

A hygroscopic insulator field-effect transistor (HIFET) ring oscillator with three inverters was built and tested under ambient laboratory conditions. An operating voltage of −2 V was used, yielding a peak-to-peak output voltage of 1.1 V and an oscillation frequency of 28 mHz. For Spice (simulation program with integrated circuit emphasis) simulation of the HIFET circuits the measured HIFET output characteristics were fitted to a DC (direct current) model and additional measurements were made to find the magnitude of the capacitive and resistive elements in the HIFET gate structure. The results indicated that HIFETs have a good potential for use in amplifier and sensor circuit applications where high operation speed is not crucial.

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► An organic HIFET ring oscillator worked with low operating voltages in ambient air.
► A simulation model for HIFET was developed based on electrical measurements.
► Capacitances related to gate structure do not explain the slow operation of HIFETs.
► The operational slowness is related to the electrochemical doping process.