Crystal Oscillator Feedback Circuit for High Frequency, Low Current
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Solution Overview
Problem
High-frequency crystal oscillator circuits face challenges in achieving high performance and low current consumption, leading to increased cost and complexity due to the need for improved semiconductor processes.
Innovation Solution
A crystal oscillator circuit design featuring an amplifying unit with odd-numbered stages of inverters connected in cascade, a first feedback resistor, and a linear amplifier with a second feedback resistor that sets conductance levels to optimize frequency performance and reduce current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the crystal oscillator circuit uses high-frequency oscillation to meet microcomputer speed requirements, then the oscillation frequency is improved, but the current consumption increases
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the conductance values of feedback resistors (Rf1, Rf2) and load capacitors (Cg, Cd) to optimize the oscillation characteristics. By changing these circuit parameters, the circuit achieves high-frequency oscillation while controlling current consumption through precise impedance matching and feedback network design
Solution Approach 2:
The patent uses feedback mechanisms through feedback resistors Rf1 and Rf2 connected in parallel with the crystal resonator and amplifying unit. These feedback elements provide negative feedback to stabilize the oscillation amplitude and frequency, enabling high-frequency operation with reduced current consumption by optimizing the feedback network's energy efficiency
2Reliability
If the oscillator circuit achieves high performance in frequency accuracy and temperature deviation, then the frequency stability is improved, but the device complexity increases
Solution Approach 1:
The patent segments the oscillator circuit into distinct functional blocks: an amplifying unit with specific odd-numbered inverter stages, feedback network with resistors Rf1 and Rf2, and load capacitors Cg and Cd. This segmentation allows each component to be optimized independently for frequency accuracy and temperature stability while maintaining overall circuit simplicity through modular design
Solution Approach 2:
The patent applies local quality by assigning specific conductance relationships to different parts of the circuit: the linear amplifier has conductance larger than the input stage inverter but equal to or less than the output stage inverter. This localized optimization of conductance values in specific circuit regions achieves frequency stability without requiring complex circuitry throughout the entire oscillator
3Use of energy by moving object
If the circuit reduces current consumption for low-power electronic devices, then the energy efficiency is improved, but the performance of downsized crystal resonators becomes insufficient
Solution Approach 1:
The patent uses parameter changes by optimizing the conductance values of feedback resistors and the capacitance values of load capacitors to match the characteristics of downsized crystal resonators. By adjusting these parameters, the circuit achieves low current consumption while maintaining adequate oscillation performance with smaller resonators that have lower energy requirements
Solution Approach 2:
The patent applies self-service through the feedback network where resistors Rf1 and Rf2 automatically adjust the energy distribution in the circuit. The feedback mechanism self-regulates to provide sufficient drive to the crystal resonator at minimal current consumption, allowing the circuit to adapt to downsized resonators without external optimization
Data Source
AI summary
An oscillator circuit includes an amplifying unit and a first feedback resistor. The amplifying unit includes an inverter at an input stage being connected to the one end of a crystal resonator, an inverter at an output stage being connected to the other end of the crystal resonator, and a linear amplifier. The linear amplifier is connected between an output terminal of the inverter at the input stage and an input terminal of the inverter at the output stage. The linear amplifier includes at least one inverter and a second feedback resistor. The second feedback resistor is connected in parallel to the at least one inverter. The linear amplifier has a conductance with a magnitude larger than a conductance of the inverter at the input stage and equal to or less than a conductance of the inverter at the output stage.