Oscillator Variable Capacitance Circuit for Frequency Sensitivity
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Solution Overview
Problem
In circuit devices that oscillate vibrators, the frequency variable sensitivity decreases when the load capacitance of the oscillation circuit increases due to parasitic capacitance, making it difficult to achieve desired frequency adjustments while maintaining circuit miniaturization.
Innovation Solution
The circuit device incorporates a variable capacitance circuit with a first and second transistor, where different reference voltages are supplied to their gates and impurity regions, and a capacitance control voltage is shared among common impurity regions of both transistors, allowing for effective adjustment of load capacitance and improved linearity of capacitance change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable capacitance circuit using transistors is used to adjust oscillation frequency, then frequency adjustment capability is improved, but frequency variable sensitivity decreases when load capacitance increases due to parasitic capacitance
Solution Approach 1:
The variable capacitance circuit is divided into multiple transistor units (first transistor unit, second transistor unit, third transistor unit) with different threshold voltages. Each unit contributes differently to the total capacitance, allowing fine-grained frequency adjustment. This segmentation enables the circuit to maintain frequency variable sensitivity even when load capacitance is large, as the distributed capacitance control reduces the impact of parasitic capacitance from any single transistor.
2Stability of the object's composition
If load capacitance is increased to improve oscillation stability, then oscillation stability is improved, but frequency variable sensitivity decreases due to parasitic capacitance effects
Solution Approach 1:
The invention changes the threshold voltage parameter of transistors by applying different reference voltages to their gates. The first transistor unit receives a first reference voltage, the second transistor unit receives a second reference voltage, and the third transistor unit receives a third reference voltage. This parameter differentiation allows each transistor unit to operate in different capacitance ranges, enabling the circuit to maintain frequency variable sensitivity across a wide load capacitance range while ensuring oscillation stability.
3Area of moving object
If circuit size is reduced for miniaturization, then device compactness is improved, but the ability to accommodate multiple transistors with different threshold voltages becomes more difficult
Solution Approach 1:
Multiple transistor units with different threshold voltages are merged into a single variable capacitance circuit architecture. The first, second, and third transistor units are connected in parallel to the load capacitance, sharing common control terminals. This merging allows the circuit to achieve a wide frequency adjustment range while maintaining a compact structure, as all transistor units work together to provide the total variable capacitance needed for frequency tuning.
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 configuration enhances frequency variable sensitivity and reduces the circuit size, enabling precise frequency adjustments without increasing the load capacitance or circuit area, thus achieving miniaturization and improved temperature compensation.
Implementation Method 1
due to a parasitic capacitance of the transistor, there is a problem in that a frequency variable sensitivity decreases when a load capacitance of the oscillation circuit increases
Implementation Method 2
a variable capacitance circuit capable of ensuring linearity of frequency a change with respect to a control voltage change is realized
Data Source
AI summary
Provided is a circuit device including: an oscillation circuit oscillating a vibrator, in which the oscillation circuit includes a variable capacitance circuit having a first variable capacitance element and a second variable capacitance element constituted by a first transistor and a second transistor, and a reference voltage supply circuit. The first reference voltage is supplied to a first gate of the first transistor and a capacitance control voltage is supplied to a first impurity region of the first transistor, the second reference voltage is supplied to a second gate of the second transistor and the capacitance control voltage is supplied to a second impurity region of the second transistor, and the capacitance control voltage is supplied to a first common impurity region of the first transistor and the second transistor.