Low-voltage-operating organic complementary inverters and ring oscillators were fabricated using high field effect mobility pentacene and C-60 thin-film transistors (TFTs). The mobilities of pentacene and C-60 TFTs were 0.44 and 0.61 cm(2)/V s, respectively. The complementary inverters composed of these TFTs operated in the voltage range of 2-10 V with large gain values up to 65. The inverter yields 5-stage ring oscillators with a high oscillation frequency of 80 Hz at 10 V. (C) 2008 Elsevier B.V. All rights reserved.