Abstract
We design and demonstrate an oscillator circuit based on feedback and controlled by a single organic transistor. Oscillations are assisted by standard operational amplifiers. The oscillator frequency f partly depends on the parameters of the circuit, but also on the transistor's channel length and charge carrier mobility. Monitoring f provides a fast and simple tool in following the change in semiconductor mobility under changing environmental conditions. We demonstrate the application of the circuit for cheap, portable organic transistor-based odor sensors. (c) 2008 American Institute of Physics.