Dithering Switch Amplifier Layout for Low-Offset Display Drivers
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Solution Overview
Problem
Conventional display driving circuits with amplifiers as buffers require a large number of MOS transistors and dithering switches, leading to increased layout area due to non-correspondence and non-uniformity in transistor characteristics during manufacturing, which affects operational characteristics and offsets.
Innovation Solution
A display driving circuit with an amplifier having an input stage, bias stage, and output stage, utilizing a minimum number of MOS transistors and dithering switches, where the input stage determines voltage levels using four path selecting switches and two input transistors, the bias stage generates class AB output voltages with current mirrors and ten path selecting switches, and the output stage uses coupling capacitors and push-pull transistors to minimize layout area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional amplifiers with multiple MOS transistors and dithering switches are used to compensate for manufacturing variations, then offset reduction is achieved, but layout area increases
Solution Approach 1:
The patent combines the dithering switch functionality directly into the amplifier structure, merging the offset compensation mechanism with the signal processing path. This integration eliminates the need for separate dithering switch circuits while achieving the same offset reduction effect, thereby reducing overall layout area.
Solution Approach 2:
The amplifier structure is designed to perform multiple functions: signal amplification, offset compensation through dithering, and manufacturing variation tolerance. By making the amplifier multi-functional, separate compensation circuits are eliminated, reducing the total number of components and layout area.
2Manufacturing precision
If a larger number of dithering switches are added to the amplifier, then offset compensation improves, but device complexity increases
Solution Approach 1:
The dithering switches are merged into the existing amplifier transistor structure rather than being added as separate external components. This integration achieves offset compensation with minimal additional complexity by reusing existing circuit elements.
Solution Approach 2:
The amplifier employs dynamic switching of transistor paths to compensate for offset. By dynamically alternating between different transistor paths during operation, the circuit achieves offset compensation without requiring a large static number of switches, thereby reducing device complexity.
Data Source
AI summary
An amplifier and a display driving circuit. The amplifier includes an input stage, a bias stage and an output stage. The input stage determines voltage levels of two nodes in correspondence to two input voltages received in response to a first bias voltage, and includes four path selecting switches, two input transistors and one bias transistor. The bias stage generates two class AB output voltages which correspond to the voltage levels of the two nodes, and includes current mirrors, ten path selecting switches, class AB bias circuits and two bias transistors. The output stage generates an output voltage VOUT that corresponds to the two class AB output voltages, and includes two coupling capacitors and two push-pull transistors. The plurality of path selecting switches operate by one signal of a first path selecting signal and a second path selecting signal that are exclusively enabled with respect to each other.