Transfer Gate Charge Compensation for Feedthrough Noise
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Solution Overview
Problem
Feedthrough noise in transistor switches affects signal accuracy and display quality due to unequal parasitic capacitors in P-type and N-type transistors, leading to charge injection and discharge issues when the switch is turned off, especially at varying input voltages.
Innovation Solution
A circuit device with a transfer gate comprising a P-type and N-type transistor in parallel, coupled with a charge compensation circuit that performs charge discharge or injection based on the input signal voltage range, controlled by a control circuit to mitigate feedthrough noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transfer gate with P-type and N-type transistors is used as a switch, then the switch can be turned off to block signal transmission, but feedthrough noise is generated due to unequal parasitic capacitors causing charge injection or discharge
Solution Approach 1:
The feedthrough noise compensation circuit pre-calculates the expected noise amount based on the input signal voltage and applies a compensating voltage in advance to counteract the feedthrough noise before it degrades the signal. The control circuit determines the input voltage level and selects appropriate compensation values to neutralize the charge injection or discharge effect.
Solution Approach 2:
The system continuously monitors the input signal voltage to the transfer gate and uses this information to dynamically adjust the compensation voltage applied by the feedthrough noise compensation circuit. This feedback mechanism ensures that the compensation remains accurate as the input voltage changes, maintaining signal integrity across different operating conditions.
2Device complexity
If equal transistor sizes are used for P-type and N-type transistors in the transfer gate, then the parasitic capacitors are equal, but feedthrough noises do not cancel out because the parasitic capacitor fluctuation characteristics are reversed between P-type and N-type transistors
Solution Approach 1:
The system changes the voltage parameter of the input signal to the transfer gate and uses this voltage information to adjust the compensation parameters in the feedthrough noise compensation circuit. By adapting the compensation voltage based on the input voltage level, the system effectively counteracts the feedthrough noise that cannot be canceled by simple transistor size matching.
3Adaptability or versatility
If the input voltage to the transfer gate varies, then the parasitic capacitor values change, but this causes voltage-dependent feedthrough noise that affects display quality
Solution Approach 1:
The feedthrough noise compensation circuit dynamically adjusts its compensation voltage based on the real-time input voltage level to the transfer gate. As the input voltage changes, the control circuit detects this change and modifies the compensation signal accordingly, ensuring that display quality remains consistent across the entire operating voltage range.
Solution Approach 2:
The system continuously monitors the input signal voltage and uses this feedback to dynamically adjust the compensation voltage applied by the feedthrough noise compensation circuit. This ensures that the compensation remains accurate as the input voltage changes, maintaining signal integrity and display quality across different operating conditions.
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
The solution effectively reduces feedthrough noise by compensating for voltage-dependent parasitic capacitor differences, improving signal accuracy and display quality by controlling charge injection and discharge during switch operation.
Implementation Method 1
charge discharge or charge injection occurs with respect to a source or a drain of the transistor via a parasitic capacitor of the transistor
Data Source
AI summary
A circuit device includes a transfer gate, a charge compensation circuit, and a control circuit. The control circuit controls the charge compensation circuit. The charge compensation circuit discharges charge from an output node of the transfer gate when a voltage of an input signal to the transfer gate is in a first voltage range at a timing at which the transfer gate is turned off. The charge compensation circuit injects charge into the output node of the transfer gate when a voltage of the input signal to the transfer gate is in a second voltage range lower than that in the first voltage range at a timing at which the transfer gate is turned off.