Ring oscillator circuits based on junction field‐effect transistors as well as metal–semiconductor field‐effect transistors with ZnO channels are presented. Single stage delay times down to 110 ns are observed. The experimental oscillation frequencies are related to easily measurable device properties by a simple analytical model. This work proves the feasibility of low power oxide based circuits with Schottky diode and bipolar (pn‐) diode gates since both approaches provide significantly lower operation voltages at similar frequencies compared to previously reported oxide thin film transistors based on insulating gates.