Op-Amp Offset Calibration Using Latched Binary Adjustment
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Solution Overview
Problem
Conventional offset adjustment circuits in TFT-LCD source driver circuits require large-scale circuits and frequent refreshing processes, leading to increased chip size and production costs, and are not suitable for high-speed continuous voltage output required by modern liquid crystal panels.
Innovation Solution
An offset adjustment device that uses a binary logical signal to adjust the offset of operational amplifier output voltages, allowing for small-scale circuit design without frequent refreshing, by short-circuiting the non-inverting and inverting input terminals and using a latch section to store and output the logical signal for offset correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional offset adjustment circuits are used, then offset adjustment is achieved, but circuit scale increases and frequent refreshing is required
Solution Approach 1:
The patent extracts only the essential function of offset detection and adjustment, removing unnecessary circuit components. The offset adjustment circuit is reduced to minimal elements: a switching element to short-circuit input terminals, a storage element to hold the offset voltage, and basic switching control, eliminating complex refreshing mechanisms while preserving offset compensation capability
Solution Approach 2:
The patent uses a storage element to create an electrical copy of the offset voltage rather than continuously measuring and adjusting it. This copied voltage representation allows the circuit to maintain offset compensation without active refreshing, reducing circuit complexity while achieving the same precision effect
2Manufacturing precision
If conventional offset adjustment circuits are used, then offset variation is reduced, but chip size increases
Solution Approach 1:
The patent removes unnecessary circuit components from conventional offset adjustment designs, keeping only the essential elements needed for offset compensation. This extraction approach maintains offset variation control while minimizing the area occupied by the offset adjustment circuit on the chip
Solution Approach 2:
The patent merges the offset storage function with existing circuit elements in the operational amplifier structure, integrating the offset compensation mechanism into the core amplifier circuit rather than adding separate dedicated components, thereby reducing overall chip size
3Manufacturing precision
If conventional offset adjustment circuits are used, then offset adjustment is achieved, but continuous high-speed voltage output is prevented
Solution Approach 1:
The patent performs offset detection and adjustment in advance during an initialization phase, storing the offset voltage in a storage element before normal operation begins. This preliminary action allows the main operational amplifier to operate continuously at high speed without interruption for offset refreshing
Solution Approach 2:
The patent implements offset adjustment as a periodic initialization operation rather than a continuous process. The switching element periodically updates the stored offset voltage during initialization phases, allowing continuous high-speed voltage output during normal operation while maintaining offset compensation
Data Source
AI summary
In one embodiment of the present invention, an operational amplifier circuit, a switching element is closed and a switching element is opened. A latch circuit DL latches an output voltage of an operational amplifier and supplies a Q output corresponding to the output voltage. A control circuit supplies an offset adjustment signal to an offset adjustment input terminal OR of the operational amplifier, thereby adjusting an offset of the output voltage. The latch circuit DL latches again the output voltage thus adjusted and minutely adjusts the offset adjustment signal so as to adjust the remaining offset. Weighting is carried out in accordance with how many times latching has been carried out, and the offset of the output voltage of the operational amplifier is quantized, thereby obtaining a binary logical signal and storing the signal in the control circuit.