Stable, Self-Biased and High-Gain Organic Amplifiers with Reduced Parameter Variation Effect

This paper presents the design and implementation of differential and self-biased single-ended high-gain amplifiers based on p-channel organic thin-film transistors (TFTs) and thin- film carbon resistors (TFCRs). Using resistive bias circuitry, the effect of mobility degradation due to aging is significantly reduced from 43% to 2.7% and 7.9% during 2 and 7 months, respectively. In addition, the bias-point instability due to bias-stress-induced threshold-voltage shifts, which can have large time constants, is limited to 9.6%. The circuits become also nearly insensitive to light. Differential and self-biased single-ended amplifiers with resistive load and bias circuitry are implemented having a gain of 29.4 dB and 23.1 dB and a gain-bandwidths (GBW) of 6.9 kHz and 2.4 kHz, respectively. An input-referred offset (Vos) of 2 mV is achieved. Due to the small footprint of the TFCRs, the circuit area is significantly reduced.