Equivalent circuit for an organic field-effect transistor from impedance measurements under dc bias

The output and forward transfer impedance of an organic field-effect transistor have been measured by a lock-in amplifier technique. The small-signal ac response of a pentacene FET, under dc bias, is used to construct the equivalent circuit. The output impedance parameters are numerically simulated using Bode plot analysis and the deviations at low frequency are modeled with contact impedance of the source-drain channel. The ac current generator at the output is estimated along with the gate capacitances.