This paper presents a sub-circuit consisting of three thin film transistors (TFTs) where the aspect ratio of the TFTs is set by the physics of the device, in particular, the defect state density. When placed in a black-box, the sub-circuit’s current–voltage characteristics closely resemble those of a single conventional TFT (a pseudo-TFT). However, the sub-circuit provides the circuit designer the ability to set the threshold voltage of this pseudo-TFT by setting the voltage of a node. This subcircuit is therefore called the Tunable Threshold Thin Film Transistor (TTT). The paper describes the theory behind the working of the TTT and realizes the sub-circuit using organic TFTs on flexible polycarbonate substrates. Among several suggested applications, the use case of balancing an asymmetric inverter by tuning the TTT is demonstrated.
Ranjan et al. (Tue,) studied this question.