Frequency Performance of Ring Oscillators Based on a-IGZO Thin-Film Transistors

Ring oscillators based on indium gallium zinc oxide thin film transistors are fabricated on glass substrates. The oscillator circuit consists of seven delay stages and an output buffer inverter. The element inverter exhibits a voltage gain higher than ?6 V/V and a wide output swing close to 85% of the full swing range. The dynamic performance of the ring oscillators is evaluated as a function of supply voltage and at different gate lengths. A maximum oscillation frequency of 0.88 MHz is obtained for a supply voltage of 50 V, corresponding to a propagation delay of less than 85 ns/stage.