This paper presents a new approach for driving an organic light emitting diode (OLED) pixel circuit using organic thin film transistor (OTFT). Depending on the linear relation between the current passing through the OLED and its luminosity and relying on Weber's law which states that the sensation of the eye to the change in brightness is logarithmic to the change itself an improved column driver is proposed. An exponential stage is added to the column driver after the digital to analog converter (DAC) block to supply the pixel circuit with exponential current. The design is done with OTFT (n-type and p-type). The model is extracted according to the current technology of organic electronics.