This letter presents organic thin-film-transistors (OTFT) using the small organic molecule Pentacene targeting applications like radio controlled identification tags. Simple OTFTs as well as inverter circuits based on a pconducting silicon wafer substrate are presented. Comparing PECVD oxide and LTO as dielectric, only LTO deposited layers provide sufficient electrical stability. PECVD oxides show defects called “pin-holes", leading to short circuiting through the gate dielectrics. OTFTs of L=1µm/W=1000µm were prepared providing I_ds = 61µA at –40V_ds and –40V_gs, a subthreshold slope of 10.3 V/dec and an on-offratio of 10². The inverter circuits using insulated gate contacts switch from V_A=–10V to V_A=–3V output voltage when the input voltage is varied from V_E=0V to V_E=–8V at a supplied voltage of V_B=–10V.