Study And Design Of Integrated Circuits Based On Metal Oxide Thin Film Transistors

Thin Film Transistor（TFT）is one of the key technologies to realize flexible electronics.In emerging applications such as internet of things,artificial intelligence,wearable health,and medical treatment,the demand for TFT integrated circuits will become more and more extensive.However,the characteristics of TFT technologies（such as lack of complementary devices and poor device electrical performance）bring challenges to circuit design.As a result,the performance of TFT integrated circuits is far from that of silicon-based CMOS circuits,and is far from practical.Therefore,it is of great significance to study TFT integrated circuits.In terms of TFT digital integrated circuits,this thesis studies code generators and amplitude shift keying（ASK）demodulators for flexible flexible radio frequency indentification（RFID）tags.In terms of TFT analog integrated circuits,this thesis studies frontend amplifiers and analog-to-digital converters（ADCs）for flexible sensing systems.The circuits are implemented by an n-type metal oxide TFT（MO-TFT）technology on a glass substrate.This thesis is organized as follows:1、In terms of RFID code generator study,this thesis analyses diode load,zero-Vgs load,capacitive bootstrap,and pseudo-CMOS logic designs.Since the pseudo-CMOS logic has the characteristics of large output swing and noise margin,basic logic gate circuits such as inverters,NOR gates,NAND gates,D latches,D flip-flops,and ring oscillators are implemented with the pseudo-CMOS logic.Measurement results show that the functionality of the circuits is correct.Output swing and noise margin of the circuits are respectively as high as 95%VDD and 25%VDD.Operating frequency of the circuits is as high as several tens of thousand Hz.Then,a 16 bit RFID code generator is realized by using pseudo-CMOS logic gates.Measurement results show that the functionality of the circuit is correct.Output data rate is as high as 28.5kbit/s and the power consumption is as low as 0.2 m W.The circuit performance is competitive with state-of-the-art counterparts.2、In terms of ASK demodulator study,this thesis proposes for the first time a ASK demodulator design based on MO-TFT.It consists of only n-type transistors and can detect ASK signals with low modulation depth.It has a novel structure which consists of a rectifier,a low-pass filter,a comparator,and an output buffer.Measurement results show that it can support minimum modulation depth of 15%,which is 40%lower than that of state-of-the-art counterparts.It can support maximum envelope rate of 8 kbit/s,which is about 2 times higher than that of state-of-the-art counterparts.The minimum internal voltage of the circuit is 2.5 V,which is 20%lower than that of state-of-the-art counterparts.3、In terms of frontend amplifier study,this thesis proposes an AC-coupling,open loop,external-biased,and capacitive bootstrap MO-TFT frontend amplifier design.Measurement results show that circuit area is 41 mm²,the power consumption is 0.1 m W（8V）,the gain is 20 d B,the bandwidth is 3 Hz～6 k Hz,the common mode rejection ratio is 42 d B,the input impedance is 100 MΩ,the input reference noise is 106μV_rms,the noise efficiency factor is 248,and the power efficiency factor is 4.9×10⁵.These performances are comparable among the state-of-the-art counterparts.The amplifier is successfully used to measure the heart-rate signal,which demonstrates its practicality.4、In terms of ADC studies,this thesis has carried out two aspects of work.One the one hand,this thesis proposes a novel voltage-controlled oscillator（VCO）-Based ADC design that is compatible with the popular unipolar,sigle-gate,and enhancement-mode TFT technologies.The ADC consists of a VCO and a counter.The VCO has a novel topology which consists of a ring oscillator,a voltage-controlled delay unit,and a level-shifter.Simulation results show that the figure of merit（Fo M）is 33 n J/c.s.,the effective number of bits（ENOB）is 4.7 bits,the sampling rate is 25 Hz,and the power consumption is 43μW（10V）.On the other hand,this thesis proposes for the first time a discrete-time TFTΣΔmodulator design using the switched capacitor technology.It consists of four differential amplifiers.One amplifier forms a switched capacitor integrator and the three other amplifiers are cascaded to form a comparator.The differential amplifier consists of a main amplification stage with positive feedback scheme and an output stage.Simulation results show that the Fo M is 107 n J/c.s.,the ENOB is 6.4 bits,the bandwidth is 22 Hz,and the power consumption is 400μW（10V）.Performances of the above circuits are competitive with those of the state-of-the-art counterparts.The study results of this thesis can provide reference for the circuit design of TFT RFID tags and TFT sensing systems.The proposed circuit topologies and design ideas open up new perspectives and possibilities for the study of TFT integrated circuits.