A characterization of the a-Si: H thin-film transistor (TFT) under varying ambient temperature is essential to the successful design of any circuit that uses a-Si:H TFTs as analog devices. In this study, a multitude of a-Si: H TFTs under different manufacturing processes as well as varying sizes are subjected to temperatures ranging from -40 to 100 degrees C while their transfer characteristics are being measured. The collected data are used to extract the various parameters that govern the TFT's characteristics such as power parameter (alpha), threshold voltage (V-t), and effective mobility (mu(eff)). The parameters are analyzed to retrieve their dependence on ambient temperature, which is subsequently incorporated in VERILOG-A to expedite circuit designs and analysis under diverse temperature environments. (c) 2006 American Vacuum Society.