Series-Coupled Varactor Circuit for 1 aF Capacitance Steps
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Solution Overview
Problem
Existing variable capacitance devices are unable to achieve a low step size of 1 aF and often require complex implementations, consuming significant chip area.
Innovation Solution
A variable capacitance device comprising series-coupled transistors with control circuitry that generates specific control signals to activate or deactivate the transistors, allowing for precise capacitance variation between nodes, with additional transistors and capacitors to enhance capacitance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing variable capacitance device solutions are used, then implementation is possible, but step size cannot achieve 1 aF or less
Solution Approach 1:
The variable capacitance device is segmented into multiple discrete capacitance elements (first capacitance element and second capacitance element) that can be independently controlled. Each element is associated with a separate control electrode, allowing individual activation or deactivation. This segmentation enables precise control over the total capacitance by selecting specific combinations of elements, achieving fine step sizes of 1 aF or less while maintaining reliability across operating conditions.
2Manufacturing precision
If complex implementation is used to achieve low step size, then capacitance control precision improves, but device complexity increases
Solution Approach 1:
Multiple capacitance elements are merged into a single variable capacitance device structure, sharing common electrodes (first electrode, second electrode, third electrode) while having additional control electrodes. This merging approach allows the device to achieve low step sizes through combinatorial control of elements without requiring completely separate control circuits for each element, thereby reducing overall implementation complexity while maintaining precision.
3Manufacturing precision
If complex implementation is used to achieve low step size, then capacitance control precision improves, but chip area consumption increases
Solution Approach 1:
The control electrodes serve multiple functions: they act as both control elements for activating/deactivating specific capacitance elements and as structural components of the device. The first electrode, second electrode, and third electrode are shared across multiple capacitance elements, reducing the total number of discrete components needed. This multi-functionality enables precise capacitance control with minimal chip area consumption.
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 achieves a low step size of 1 aF or less with a simplified implementation, enabling fine capacitance tuning and efficient use of chip area.
Implementation Method 1
Each transistor has certain parasitic capacitances associated therewith... gate-drain capacitance, gate-source capacitance, drain-bulk capacitance and source-bulk capacitance
Data Source
AI summary
A variable capacitance device including: first and second transistors coupled in series by their main current nodes between first and second nodes of the device, a control node of the first transistor being adapted to receive a first control signal, and a control node of the second transistor being adapted to receive a second control signal; and control circuitry adapted to generate the first and second control signals from a selection signal.