Amplifier Offset Compensation Using Threshold Pre-Charging
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Solution Overview
Problem
The calibration process of operational amplifiers in integrated circuits is slow due to long transition times between voltage levels, caused by low output current charging parasitic capacitances, which delays the start-up phase of the integrated circuit.
Innovation Solution
A method that couples the negative and positive inputs of the operational amplifier to the same voltage level, using a current-to-voltage converter to generate a control voltage that quickly switches and biases the output to a threshold voltage, allowing for rapid compensation of internal voltage offsets through a trigger signal and a gradually adjusted compensation signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the amplifier uses low output current to charge parasitic capacitances, then the circuit operates stably with proper frequency compensation, but the transition time between voltage levels becomes long
Solution Approach 1:
The patent applies preliminary action by pre-charging the parasitic capacitances to a threshold voltage level before the actual calibration transition. This is achieved by coupling the negative and positive inputs to the same voltage level, which pre-charges the output node capacitance, so that when the calibration transition occurs, the amplifier does not need to charge the full capacitance from zero, significantly reducing the transition time while maintaining stability
Solution Approach 2:
The patent changes the operating parameters of the amplifier during calibration by dynamically adjusting the input voltage levels. Specifically, it couples the inputs to the same voltage level during calibration mode, which changes the operating point and allows faster transitions. This parameter change enables the amplifier to switch between stable operation mode and fast calibration mode
2Measurement precision
If the amplifier operates as a comparator during calibration with inputs short-circuited, then offset voltage can be detected, but the calibration phase takes significant time
Solution Approach 1:
The patent applies preliminary action by pre-charging the output node capacitance to a threshold voltage before offset detection. This preliminary charging state is achieved by coupling the inputs to the same voltage level, which allows the subsequent offset voltage transition to occur faster since the capacitance is already charged and only needs to discharge or charge a small amount to detect the offset, rather than charging from zero
Solution Approach 2:
The patent implements skipping by rapidly transitioning the amplifier through the calibration state. By pre-charging the capacitances and using a threshold voltage reference, the system can quickly detect the offset voltage transition without waiting for slow charging of parasitic capacitances, effectively rushing through the calibration phase while maintaining detection accuracy
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
This approach significantly reduces the calibration time by pre-charging parasitic capacitances and enabling faster detection and compensation of voltage shifts, thereby accelerating the calibration process and reducing the overall duration of the calibration phase.
Implementation Method 1
biasing the output of the first amplifier to a threshold voltage, with a current-to-voltage converter, and generating a control voltage with the current-to-voltage converter comprising the sum of the threshold voltage and a voltage conversion of the comparison current
Data Source
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AI summary
A method for compensating an internal voltage offset between a positive input (Vcomp+) and a negative input (Vcomp-) of a first amplifier (COMP), comprising coupling the negative input (Vcomp-) and the positive input (Vcomp+) of the first amplifier (COMP) to the same voltage level, so as to generate a comparison current (Iout1) on an output of the first amplifier (OUT1), the sign of the comparison current being representative of the sign of the internal voltage offset (Voffs) on the inputs of the first amplifier (Vcomp+, Vcomp-), biasing the output (OUT1) of the first amplifier to a threshold voltage (Vref), with a current-to-voltage converter (CONV), and generating a control voltage (Vout2) comprising the sum of the threshold voltage (Vref) and a voltage conversion of the comparison current (Iout1), compensating for the internal voltage offset (Voffs) between the inputs of the first amplifier (Vcomp+, Vcomp-).depending on the control voltage (Vout2).