CMOS Level Shifter Circuit for Low-Amplitude Signal Reliability
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Solution Overview
Problem
Level shifter circuits formed on glass substrates for liquid-crystal or electroluminescent display units face challenges in amplifying low-amplitude signals due to large fluctuations in transistor threshold voltage, leading to operational failures and increased EMI noise.
Innovation Solution
A level shifter circuit comprising a CMOS inverter with p-type and n-type transistors, capacitors, and switches that apply reference voltages to stabilize gate voltages, allowing independent adjustment of voltages to ensure reliable operation even with low-amplitude input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a level shifter circuit is formed on glass substrate using same process as pixel transistor, then manufacturing cost is reduced and integration is improved, but transistor threshold voltage fluctuation increases and circuit reliability deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing preset voltages (first preset voltage and second preset voltage) that are different from the normal operating voltage. These preset voltages are applied to the gates of transistors during the signal amplification process, dynamically changing the electrical parameters to compensate for threshold voltage fluctuations and ensure reliable circuit operation on glass substrates
Solution Approach 2:
The patent implements preliminary action by applying preset voltages to transistors before the actual signal processing operation. The first preset voltage is applied to the first transistor and second preset voltage to the second transistor in advance, preparing the transistors to operate reliably despite threshold voltage variations inherent in glass substrate manufacturing
2Object-generated harmful factors
If low-amplitude signal is transmitted to reduce EMI noise, then radiation noise is reduced, but signal amplitude becomes insufficient for reliable circuit operation
Solution Approach 1:
The patent changes the voltage parameters dynamically by applying preset voltages during signal transmission. When a low-amplitude input signal is received, the preset voltages are applied to the transistors to amplify the signal amplitude, ensuring reliable operation while maintaining low EMI noise during normal low-amplitude transmission
3Use of energy by moving object
If transistor threshold voltage is reduced to enable lower driving voltage, then power consumption is reduced and driving voltage can be lowered, but threshold voltage control becomes more difficult and fluctuations increase
Solution Approach 1:
The patent compensates for threshold voltage control difficulties by introducing preset voltages that are applied to transistor gates. These preset voltages adjust the effective operating point of transistors, compensating for threshold voltage fluctuations caused by reduced control precision in glass substrate manufacturing while maintaining low power consumption operation
Data Source
AI summary
A level shifter circuit which amplifies the amplitude of an input signal, includes a CMOS inverter which is composed of a p-type transistor and an n-type transistor, a first and a second capacitor one electrode of each of which is connected to the gate of the p-type transistor and that of the n-type transistor, respectively, a first switch which supplies the input signal to the other electrodes of the first and second capacitors, a second switch which applies a direct-current voltage whose amplitude is nearly half of the amplitude of the input signal to the other electrodes of the first and second capacitors, and a third and a fourth switch which apply a first and a second preset voltage to one electrode of each of the first and second capacitors, respectively.