Record Details

Threshold Voltage Shift Compensating Circuits in Non-Crystalline Semiconductors for Large Area Sensor Actuator Interface

Electronic Theses of Indian Institute of Science

View Archive Info
 
 
Field Value
 
Title Threshold Voltage Shift Compensating Circuits in Non-Crystalline Semiconductors for Large Area Sensor Actuator Interface
 
Creator Raghuraman, Mathangi
 
Subject Sensor Actuator Interface
Non-Crystalline Semiconductors
Thin Film Transistor (TFT)
Semiconductors
Threshold Voltage Shift (VT)
Circuit Simulators
Tin Doped Zinc Oxide Thin Film Transistors
Copper Phthalocyanine Thin Film Transistors
Sensors and Actuators
Interface Circuits
VT Shift Model
Thin Film Transistors (TFTs)
Sensor Actuator System
Threshold Voltage (VT)
VT Shift Model
Electronics Engineering
 
Description Thin Film Transistors (TFTs) are widely used in large area electronics because they offer the advantage of low cost fabrication and wide substrate choice. TFTs have been conventionally used for switching applications in large area display arrays. But when it comes to designing a sensor actuator system on a flexible substrate comprising entirely of organic and inorganic TFTs, there are two main challenges – i) Fabrication of complementary TFT devices is difficult ii) TFTs have a drift in their threshold voltage (VT) on application of gate bias. Also currently there are no circuit simulators in the market which account for the effect of VT drift with time in TFT circuits.
The first part of this thesis focuses on integrating the VT shift model in the commercially available AIM-Spice circuit simulator. This provides a new and powerful tool that would predict the effect of VT shift on nodal voltages and currents in circuits and also on parameters like small signal gain, bandwidth, hysteresis etc. Since the existing amorphous silicon TFT models (level 11 and level 15) of AIM-Spice are copyright protected, the open source BSIM4V4 model for the purpose of demonstration is used. The simulator is discussed in detail and an algorithm for integration is provided which is then supported by the data from the simulation plots and experimental results for popular TFT configurations.
The second part of the thesis illustrates the idea of using negative feedback achieved via contact resistance modulation to minimize the effect of VT shift in the drain current of the TFT. Analytical expressions are derived for the exact value of resistance needed to compensate for the VT shift entirely. Circuit to realize this resistance using TFTs is also provided. All these are experimentally verified using fabricated organic P-type Copper Phthalocyanine (CuPc) and inorganic N-type Tin doped Zinc Oxide (ZTO) TFTs.
The third part of the thesis focuses on building a robust amplifier using these TFTs which has time invariant DC voltage level and small signal gain at the output. A differential amplifier using ZTO TFTs has been built and is shown to fit all these criteria. Ideas on vertical routing in an actual sensor actuator interface using this amplifier have also been discussed such that the whole system may be “tearable” in any contour. Such a sensor actuator interface can have varied applications including wrap around thermometers and X-ray machines.
 
Contributor Sambandan, Sanjiv
 
Date 2018-02-25T08:28:47Z
2018-02-25T08:28:47Z
2018-02-25
2014
 
Type Thesis
 
Identifier http://hdl.handle.net/2005/3176
http://etd.ncsi.iisc.ernet.in/abstracts/4037/G26342-Abs.pdf
 
Language en_US
 
Relation G26342