Offset Canceller Circuit for Continuous Output Compensation
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Solution Overview
Problem
Conventional offset canceller circuits for operational amplifiers in liquid crystal display device drivers cannot compensate for offsets caused by externally connected capacitive or resistance devices, and they fail to output signals during offset compensation operations.
Innovation Solution
An offset canceller system with multiple output circuits, selectors, and a decision circuit that allows for continuous signal output during offset compensation, using differential amplifiers and resistance value setting circuits to adjust and verify offset cancellations, enabling accurate and uniform voltage output across terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional offset canceller circuits are used to cancel offset voltage in operational amplifiers, then offset voltage cancellation is achieved, but offset caused by externally connected capacitive or resistance devices cannot be compensated
Solution Approach 1:
The invention changes the parameter being compensated from only offset voltage to include both offset voltage and offset caused by external capacitive or resistance devices. This is achieved by adding a compensation current source that can generate current proportional to the external device parameters, thereby extending the compensation capability while maintaining accuracy.
Solution Approach 2:
The offset cancellation function is segmented into two independent compensation paths: one for offset voltage (using traditional voltage cancellation) and another for offset caused by external devices (using current cancellation). This segmentation allows each path to be optimized independently, improving both voltage cancellation accuracy and adaptability to external devices.
2Measurement precision
If offset compensation operation is performed in conventional circuits, then offset is canceled, but no signal can be output during the operation
Solution Approach 1:
The invention maintains continuous signal output capability during offset compensation by using a switching mechanism that allows the compensation operation to occur in parallel with the signal transmission path. The compensation current is generated and applied without interrupting the main signal flow, ensuring both productivity and compensation accuracy are maintained simultaneously.
Solution Approach 2:
A switching circuit acts as an intermediary between the compensation current source and the output terminal. This switch allows the compensation current to be injected into the output path only when needed, while normally allowing the signal to pass through uninterrupted. This resolves the contradiction by enabling selective activation of compensation without permanently blocking signal output.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate offset cancellation while maintaining signal output, improving the accuracy of capacitance and resistance adjustments, and allowing for compensation without capacitive devices, ensuring consistent and precise voltage delivery.
Implementation Method 1
an operational amplifier for amplifying an input signal and for outputting an amplified signal
Implementation Method 2
a capacitive device for setting a feedback factor in a feedback path connected between the output terminal and an input terminal of the operational amplifier
Implementation Method 3
a resistance device for setting a feedback factor in a feedback path connected between the output terminal and an input terminal of the operational amplifier
Implementation Method 4
a decision circuit operative in response to the output from the plurality of output circuits for verifying the state of offset
Implementation Method 5
a differential amplifier for receiving an input signal on its one input terminal and for amplifying the input signal received
Data Source
AI summary
An offset canceller outputs a signal during its offset compensating operation and compensates for the offset by capacitance or resistance devices connected externally to an operational amplifier. A driving circuit includes plural output circuits #1 to #n+1 for outputting driving signals to plural output terminals #1 to #n on one outputs and for outputting the driving signals on the other outputs coupled to corresponding plural output selectors #1 to #n, which then select one of two signals output from two neighboring output circuits to transmit the selected signals to the output terminals. The output circuits #1 to #n+1 have other outputs coupled to a decision circuit, which compares the signals to a reference voltage and outputs a decision signal representing the result of comparison at a predetermined timing. The output circuits execute the offset cancel operation responsive to the decision signal.