Piezoelectric Oscillator Circuit Using Parasitic Capacitance for Wide Tuning
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Solution Overview
Problem
Existing oscillators with voltage-controlled oscillating frequency have limited capacitance variable range, making it difficult to achieve desired frequency changes and control, especially when integrated into IC chips, due to adverse effects from parasitic capacitance.
Innovation Solution
The oscillator design includes a semiconductor amplifier circuit, a piezoelectric resonator, and a variable capacitance element connected in series, with parasitic capacitance functioning as a bypass capacitor to allow for larger frequency changes with minimal control voltage adjustments, and the use of MOS-type variable capacitance elements for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the capacitance variable range of the variable capacitance element is extended to increase frequency change amount, then the frequency control range is improved, but the fabrication process complexity and cost increase drastically
Solution Approach 1:
The patent converts parasitic capacitance, which was previously considered an adverse effect limiting frequency control, into a beneficial component that functions as a bypass capacitor. By connecting the variable capacitance element in series with the amplifier circuit and utilizing parasitic capacitance in parallel, the system achieves wide frequency tuning range without requiring complex fabrication process revisions.
2Adaptability or versatility
If the capacitance variable range of the variable capacitance element is extended to increase frequency change amount, then the frequency control range is improved, but the development time and cost increase
Solution Approach 1:
The invention transforms parasitic capacitance from a harmful factor into a useful component, eliminating the need for extensive fabrication process revisions and simulation optimizations. This approach significantly reduces development time and cost while achieving the desired wide frequency control range.
3Adaptability or versatility
If the variable capacitance element is provided solely within the oscillating loop to maximize frequency change, then the frequency control function is improved, but parasitic capacitance adversely affects the desired frequency change amount
Solution Approach 1:
The patent repositions the variable capacitance element outside the oscillating loop and in series with the amplifier circuit, while utilizing parasitic capacitance in parallel to function as a bypass capacitor. This configuration eliminates the adverse effects of parasitic capacitance and enables effective frequency control.
Solution Approach 2:
Instead of placing the variable capacitance element within the oscillating loop as conventionally done, the patent inverts the configuration by positioning it in series with the amplifier circuit. This inversion, combined with using parasitic capacitance as a bypass capacitor, resolves the conflict between frequency control function and parasitic capacitance effects.
4Volume of moving object
If the portions in the oscillator other than piezoelectric resonator are made to be integrated circuit to reduce size, then the device miniaturization is improved, but the capacitance variable range of variable capacitance element becomes limited
Solution Approach 1:
The patent enables integration of the oscillator portions into an IC chip by utilizing parasitic capacitance inherent in the integrated circuit structure as a bypass capacitor. This approach maintains the capacitance variable range needed for wide frequency tuning while achieving device miniaturization through integration.
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 enables wide-range frequency control with reduced parasitic capacitance effects, facilitating miniaturization and improved noise properties in oscillators, even when integrated into IC chips.
Implementation Method 1
an oscillating element 32 which has a piezoelectric resonator
Implementation Method 2
a voltage variable capacitance element 39 connected between one terminal A
Implementation Method 3
an inverter amplifier circuit 31 having an inverter 34 and a feedback resistance 35
Data Source
AI summary
An oscillator, includes an amplifier circuit including a semiconductor element having a first constant potential as reference potential for a power supply voltage, a variable capacitance element, a piezoelectric resonator, and a capacitance circuit constituting a closed circuit with the piezoelectric resonator. The amplifier circuit and the variable capacitance element are connected in series to provide a series circuit. The capacitance circuit connects the capacitance elements in a plurality of numbers in series. A connecting midpoint of the series connection is connected to a circuit for the first constant potential. Two connecting midpoints other than the midpoint of the closed circuit are used as connecting points to connect the series circuit and the closed circuit in parallel.