Variable Charge Packet IC Capacitor Design
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Solution Overview
Problem
Existing integrated circuit capacitors face limitations in providing a variable or programmable capacitance range, which is often incompatible with IC processing technologies, restricting their functionality in tunable RF circuits and waveform generation.
Innovation Solution
A variable capacitor design utilizing a semiconductor layer doped with mobile charge carriers, where first and second capacitor electrodes and gate electrodes are strategically positioned with circuitry to inject and confine a 'charge packet' under the electrodes, allowing for controlled capacitance through applied potentials, enabling capacitance to be varied over several orders of magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If varactors or op amp-boosted Miller capacitances are used to provide variable capacitance in IC circuits, then capacitance can be tuned, but the capacitance range is limited and maximum capacitance is restricted
Solution Approach 1:
The patent changes the fundamental operating parameter from voltage-controlled capacitance (varactors) or amplifier-based capacitance (Miller) to charge-packet-controlled capacitance. By injecting discrete charge packets into the semiconductor layer and controlling their movement between regions, the capacitance can be varied over a much wider range while achieving higher maximum capacitance values that are compatible with IC processing.
2Ease of manufacture
If variable capacitance is provided using conventional IC-compatible methods, then the capacitor can be integrated into IC circuits, but the capacitance variation is limited to a narrow range
Solution Approach 1:
The patent replaces the electrical field-based capacitance control (varactors, Miller capacitance) with a charge transport mechanism. Mobile charge carriers are physically moved between regions of the semiconductor layer using electric fields applied through gate and source/drain electrodes, creating a mechanically-like charge packet transport system that achieves wide capacitance variation while remaining IC-compatible.
3Adaptability or versatility
If a finite charge packet is confined under capacitor electrodes, then capacitance can be controlled over several orders of magnitude, but the device complexity increases
Solution Approach 1:
The gate, source, and drain electrodes serve multiple functions: they control charge packet injection, confinement, and movement. The same electrode structure that defines the capacitor also controls the charge packet behavior, eliminating the need for separate control mechanisms and reducing overall device complexity despite the advanced functionality.
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 solution provides a highly controllable and compatible IC capacitor that can vary capacitance significantly, supporting advanced RF circuit applications by manipulating the charge packet's magnitude and location in response to RF drive signals, enhancing the range and linearity of capacitance.
Implementation Method 1
A semiconductor layer is doped to contain mobile charge carriers of a first polarity
Implementation Method 2
apply potentials to the gate electrodes such that the injected charge is confined to the region of the layer under the capacitor electrodes
Implementation Method 3
an RF drive signal voltage V applied between the capacitor electrodes causes the charge packet to move back and forth between the portion of the region below the first capacitor electrode and the portion of the region below the second capacitor electrode
Data Source
AI summary
A variable IC capacitor includes a semiconductor layer doped to contain mobile charge carriers. Capacitor electrodes C1 and C2 are disposed adjacent to each other on the layer's surface, gate electrodes G1 and G2 are disposed on opposite sides of C1 and C2, and source and sink electrodes are disposed on opposite sides of G1 and G2. Potentials are applied to the electrodes as needed to inject and then confine a finite charge into the region under C1 and C2. A drive voltage V applied between C1 and C2 causes the charge packet to move back and forth beneath them, such that the effective capacitance C seen by drive voltage V is given by C=Q/V, where Q is the magnitude of the charge packet.