Organic materials can be used to fabricate sensors for physical and chemical quantities, and also to make electronics. The integration of these two elements holds the promise to enable novel smart-sensors on foil. In this paper, we deal with the design of the first stage of a signal conditioning chain on foil: the amplifier. The poor electrical performance of organic TFTs hampers the design of complex circuits, and negatively affects the characteristics of continuous-time amplifiers. In order to improve small-signal gain and speed, a mixed discrete-time and continuous-time approach is presented in this paper for the sensor frontend. A new device, the Thin-Film Trans-Capacitor, is presented and used to build the discrete-time amplifier, while the continuous time amplifier exploits a simple traditional architecture to improve yield. Simulations of the circuit proposed show that the total gain of the sensor frontend increases of about one decade without any detrimental effect on the speed. CAD (Computer-Aided Design) simulations confirm the results of the simple mathematical model we present.