Differential Amplifier Oscillator for Power Supply Noise Rejection
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Solution Overview
Problem
Conventional oscillators are sensitive to power supply noise, resulting in high jitter and poor rejection of power supply noise, which limits their frequency range and stability.
Innovation Solution
An oscillator circuit comprising multiple differential amplifiers connected in series and an auxiliary start circuit, where the ratio of negative and positive resistance is controlled by digital signals to adjust oscillation frequency, and the auxiliary start circuit generates disturbance signals to maintain normal oscillation and widen the frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inverters are used to determine oscillation frequency, then the oscillation frequency can be determined, but the oscillator becomes sensitive to power supply noise resulting in large jitter and poor rejection effect
Solution Approach 1:
The patent changes the fundamental parameter of the oscillation determination mechanism from inverter delay to differential amplifier phase difference. By using differential amplifiers with controllable gain and phase characteristics, the system achieves frequency determination through phase comparison rather than delay, making it insensitive to power supply noise while maintaining frequency control capability
Solution Approach 2:
The patent replaces the conventional inverter-based delay mechanism with a differential amplifier-based phase comparison system. This substitution eliminates the sensitivity to power supply noise inherent in inverter circuits while achieving the same frequency determination function through phase difference measurement and control
2Adaptability or versatility
If the oscillation frequency is determined by inverter delay, then the frequency can be controlled, but the frequency range is limited
Solution Approach 1:
The patent introduces dynamic control of differential amplifier characteristics through digital-to-analog converters and variable gain stages. The system can dynamically adjust the phase difference and gain of differential amplifiers to achieve wide frequency tuning range, replacing static inverter delay with dynamically controllable phase comparison
Solution Approach 2:
The differential amplifier circuit serves multiple functions: frequency determination, phase comparison, gain control, and noise rejection. This multi-functional design achieves wide frequency range capability while avoiding the need for separate frequency control mechanisms, thereby managing complexity through functional integration
Data Source
AI summary
An oscillator circuit comprises differential amplifiers connected in series and an auxiliary start circuit. A first output terminal and a second output terminal of each differential amplifier are respectively coupled to a first input terminal and a second input terminal of the next differential amplifier. Said first output terminal of the last differential amplifier is coupled to said second input terminal of the first differential amplifier. Said second output terminal of said last differential amplifier is coupled to said first input terminal of said first differential amplifiers. Said auxiliary start circuit generates a first disturbance signal and a second disturbance signal to said first input terminal and said second input terminal of a second differential amplifier according to said signal state of said first input terminal of a first differential amplifier. Said first different amplifier is one of said differential amplifiers. Said second differential amplifier is another differential amplifier.