A complementary inverter was fabricated using pentacene and N-N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide-C8 (PTCDI-C8) for p- and n-type transistors on a poly(ether sulfone) substrate, respectively. The mobilities of the p- and n-type transistors were 0.056 and 0.013 cm2/V s, respectively. The inverter, which was composed of p- and n-type transistors, showed a gain of 48.6 when V DD=−40 V and at the maximum noise margin of V DD/2. A ring oscillator was also fabricated by cascading five inverters. The five-stage ring oscillator showed the maximum output frequency of 10 kHz when V DD=−170 V.