Relaxation Oscillator Feedback Circuit for Precise Periodic Signals
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Solution Overview
Problem
Existing relaxation oscillators struggle to generate accurate periodic signals.
Innovation Solution
A relaxation oscillator design incorporating specific transistor configurations, capacitors, resistors, and switches, along with a bandgap voltage reference circuit and operational amplifier, to generate precise periodic signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional relaxation oscillator designs are used, then the circuit structure is simple, but the periodic signal accuracy is poor
Solution Approach 1:
The oscillator circuit is divided into multiple functional modules: a current mirror circuit with first and second transistors for current regulation, a charging circuit with third transistor and resistor for controlled capacitor charging, and a discharge circuit with fourth transistor for capacitor discharge. This segmentation allows each module to be optimized independently for accuracy while maintaining overall circuit manageability.
Solution Approach 2:
The inverter connects the output back to the control terminals of the transistors, creating a feedback loop that automatically regulates the charging and discharging processes. When the capacitor voltage reaches a threshold, the inverter switches states, triggering the discharge phase, and when discharged, triggers recharge, ensuring accurate periodic operation.
2Loss of time
If traditional relaxation oscillator designs are used, then the circuit area is small, but the start-up time is long
Solution Approach 1:
The bandgap voltage reference circuit generates a stable reference voltage before the oscillation begins, and the pulse generator is pre-configured to immediately trigger the discharge phase when the capacitor reaches the threshold voltage. This preliminary preparation of voltage references and control logic eliminates start-up delays.
Solution Approach 2:
The circuit uses a bandgap voltage reference to provide a temperature-compensated reference voltage that remains stable across process variations and temperature changes. This parameter stabilization ensures consistent oscillation frequency and reduces start-up time by eliminating drift and settling delays.
3Measurement precision
If traditional relaxation oscillator designs are used, then the power consumption is low, but the periodic signal accuracy is poor
Solution Approach 1:
The oscillator uses periodic charging and discharging of the capacitor instead of continuous operation. The third transistor charges the capacitor through the resistor during one phase, then the fourth transistor discharges it during the next phase, with the inverter switching between states. This periodic action reduces average power consumption while maintaining accurate periodic signal generation.
Solution Approach 2:
The circuit automatically regulates its own operation through the feedback loop. The inverter monitors the capacitor voltage and automatically triggers the discharge phase when the threshold is reached, eliminating the need for external control signals or additional power-consuming control logic. The current mirror circuit also self-regulates the charging current based on the reference voltage.
Data Source
AI summary
A relaxation oscillator includes first to the sixth transistor, a resistor, a capacitor, an inverter, a pulse generator, and first to the third switch. The resistor is coupled between the third source and the third gate of the third transistor. The capacitor is coupled between the fourth source and the fourth gate of the fourth transistor. The input terminal of the inverter is coupled to the sixth drain of the sixth transistor. The pulse generator generates a pulse signal. The first switch is coupled between the inverter and a first reference voltage. The second switch is coupled between the inverter and the fifth transistor. The third switch is coupled between the fourth transistor and a second reference voltage. The first to third switches are turned on or off according to the pulse signal.