Amplifier Circuit with Oxide TFT

Abstract

Oxide TFT (thin film transistor) has higher electron mobility and less leakage current than amorphous silicon TFT. Among oxide TFTs such as ZnO, InZnO, InGaZnO and so on, the IGZO TFT has being studied by many researchers and being used in the display backplane. In this presentation, an amplifier circuit with oxide TFTs was developed for the higher voltage gain. Most commonly used type of power amplifier is the Class A Amplifier. The Class A amplifier is the most common and simplest form of power amplifier, in which transistor is always biased on-state so that it conducts during one complete cycle of the input signal waveform producing minimum distortion and maximum amplitude to the output. The efficiency of this type of circuit is low and delivers small power outputs. To get high amplification gain, we designed an amplifier circuit based on inverter and optimized the channel width of each TFTs. The circuit developed is a common source amplifier, which is a single transistor amplifier that the input terminal is the gate and the source, output terminal is the drain and the source. In that type of amplifier circuit, the ratio of the widths of load transistor and drive transistor should be optimized for the highest gain. The DC operating voltage for the input gate electrode is also important, and the conventional way to get the operation voltage is using resistor divider, in which we should design the resistor divider according to the characteristics of TFT. In this presentation, we proposed the auto setting operation voltage scheme instead of resistor divider, and obtained the voltage gain of 14.