Ring Oscillator Clock Circuit With Temperature-Compensated Current Control
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Solution Overview
Problem
Conventional ring oscillator circuits fail to maintain a constant oscillating frequency when environmental temperature changes, despite stabilizing the frequency against voltage fluctuations using constant current circuits.
Innovation Solution
A clock signal output circuit with a current regulating circuit that adjusts gate voltage to ensure current flowing through upper transistors is proportional to the threshold voltage of lower transistors, counteracting the effect of temperature variations on oscillating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current circuit is used to stabilize current against voltage fluctuations, then voltage stability is improved, but temperature-induced frequency drift is not compensated
Solution Approach 1:
The patent changes the operating parameters of the constant current circuit by making the current magnitude proportional to the threshold voltage of the lower transistors. This is achieved through a current regulating circuit that adjusts the gate voltage of upper transistors based on temperature-dependent threshold voltage changes, thereby compensating for temperature-induced frequency drift while maintaining voltage stability.
Solution Approach 2:
The patent implements a feedback mechanism where the current regulating circuit continuously monitors and adjusts the gate voltage of upper transistors to maintain current proportionality to threshold voltage. This feedback loop compensates for temperature variations by dynamically adjusting circuit parameters, resolving the contradiction between voltage stability and temperature compensation.
2Reliability
If gate voltage is adjusted to compensate for temperature variations, then frequency stability is improved, but circuit complexity increases
Solution Approach 1:
The current regulating circuit serves multiple functions: it maintains current proportionality to threshold voltage, compensates for temperature variations, and stabilizes oscillating frequency. By making the circuit multi-functional, the patent achieves frequency stability without proportionally increasing complexity, as a single circuit block accomplishes multiple objectives.
Solution Approach 2:
The patent achieves frequency stability by changing the gate voltage parameter dynamically based on temperature-dependent threshold voltage changes. This parameter adjustment is implemented through a relatively simple current regulating circuit that uses proportional current control, avoiding the need for complex temperature sensing and compensation mechanisms.
3Adaptability or versatility
If current magnitude is made proportional to threshold voltage, then temperature compensation is improved, but control complexity increases
Solution Approach 1:
The current regulating circuit automatically adjusts the gate voltage of upper transistors to maintain current proportionality to threshold voltage without requiring external temperature sensing or manual adjustment. The circuit serves itself by using the inherent relationship between current and threshold voltage to achieve temperature compensation, thereby avoiding complex control mechanisms.
Solution Approach 2:
The patent simplifies control by directly changing the current magnitude parameter to be proportional to threshold voltage, rather than using complex control algorithms. This straightforward parameter relationship enables temperature compensation through simple proportional control, reducing the complexity of the control mechanism while improving adaptability.
Data Source
AI summary
1st to nth pairs of transistors (n=an odd number) are connected in parallel, and each pair of transistors has an upper transistor and a lower transistor connected in series. A point between the upper transistor and the lower transistor of a preceding pair of transistors is connected to a gate of the lower transistor of a subsequent transistor, and the point between the upper transistor and the lower transistor of nth pair of transistors is connected to the gate of the first lower transistor. A capacitor is inserted between the lower transistor and a direct power source. A current regulating circuit connected to gates of the upper transistors, wherein the current regulating circuit supplies a gate voltage to each gate of the each upper transistor. The magnitude of the gate voltage is adjusted such that a magnitude of current that flows between the source and drain of the upper transistor due to the gate voltage is proportional to a voltage between the source and gate of the corresponding lower transistor when the lower transistor is turned on.