Single-Capacitor Oscillator Circuit for Stable 50% Duty Cycle
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Solution Overview
Problem
Existing oscillator circuits require multiple capacitors, which occupy a large area on a semiconductor substrate, making it difficult to design compact frequency synthesizers and digital circuits.
Innovation Solution
An oscillator circuit configuration using a single capacitor and a control circuit to switch between charging and discharging states, reducing the number of capacitors and minimizing circuit area while maintaining a 50% duty cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple capacitors are used in the oscillator circuit, then the circuit can maintain stable oscillation, but the circuit area occupied increases
Solution Approach 1:
The patent combines multiple capacitor functions into a single capacitor by using switching circuits to alternately connect the capacitor to different circuit nodes during charging and discharging phases. This merging approach maintains the oscillation stability that would otherwise require multiple capacitors while significantly reducing the circuit area occupied by capacitive elements.
Solution Approach 2:
The patent employs dynamic switching of circuit connections to achieve different functional states with a single capacitor. The switching circuit dynamically connects the capacitor to different nodes (first node, second node, third node) at different times during the oscillation cycle, enabling the capacitor to serve multiple roles that would traditionally require separate static components.
2Area of stationary object
If the number of capacitors is reduced to one, then the circuit area is minimized, but it becomes challenging to maintain 50% duty cycle and oscillation stability
Solution Approach 1:
The patent incorporates feedback mechanisms through the switching circuit that monitors the voltage at different nodes and adjusts the charging and discharging timing accordingly. This feedback control ensures that the capacitor charges and discharges for equal durations, maintaining the 50% duty cycle requirement even with a single capacitor configuration.
Solution Approach 2:
The patent uses periodic switching actions to alternately connect the single capacitor to different circuit nodes in a regular cycle. This periodic connection pattern ensures that the capacitor spends equal time charging and discharging, thereby maintaining the 50% duty cycle while using minimal capacitance area.
3Device complexity
If multiple capacitors are used, then the circuit configuration is simpler, but the frequency synthesizer design becomes more complex and less compact
Solution Approach 1:
The patent makes the single capacitor universal by enabling it to perform multiple functions through the switching circuit. The same capacitor serves as the timing element for oscillation, the duty cycle control element, and the frequency determination element, replacing what would traditionally require multiple specialized capacitors in a frequency synthesizer application.
Data Source
AI summary
A first current source and a second current source generate a first current and a second current, respectively. A first transistor is arranged with its drain coupled to the first current source and a reference voltage applied to its source. A second transistor is coupled between a first end of a capacitor and a first node. A third transistor is coupled between a second end of the capacitor and a second node. A first switch is coupled between the first node and the second current source. A second switch is coupled between the second node and the second current source. A charging/discharging circuit includes a third switch coupled between the first end of the capacitor and the ground and a fourth switch coupled between the second end of the capacitor and the ground.