Differential Amplifier Offset Regulation for Stable Common-Mode Voltage
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Solution Overview
Problem
The existing fully differential amplifier configurations lack sufficient ability to maintain common mode voltage in line with a reference voltage, leading to fluctuations in amplification and power supply instability, which affects downstream circuits and requires larger transistors for increased ability, compromising miniaturization.
Innovation Solution
An amplifier with an offset regulating circuit that feeds back a regulation signal not only to the current source of the amplification part but also to the current source of the offset regulating part, dynamically adjusting current to maintain common mode voltage stability and compensate for power supply fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transistor size is increased to improve regulation ability, then the common mode voltage can better follow the reference voltage, but the circuit area increases and miniaturization is compromised
Solution Approach 1:
The patent implements a feedback mechanism where the output of the common mode feedback part is fed back to the current source of the signal amplification part. This feedback loop enables the system to automatically adjust and maintain the common mode voltage at the reference voltage level, improving regulation ability without requiring larger transistors. The feedback signal compensates for deviations in real-time, resolving the contradiction between regulation performance and circuit size.
Solution Approach 2:
The patent changes the operating parameters of the circuit by dynamically adjusting the current source based on the feedback signal. By varying the current parameter in response to common mode voltage deviations, the system achieves better voltage following ability without physical enlargement of the transistor. This parameter-based control resolves the contradiction by using electrical parameter modulation instead of physical size increase.
2Reliability
If feedback is implemented to improve common mode voltage regulation, then the common mode voltage can follow the reference voltage better, but the device complexity increases
Solution Approach 1:
The patent applies feedback by connecting the output of the common mode feedback part back to its current source. This creates a closed-loop control system that automatically regulates the common mode voltage to match the reference voltage. The feedback mechanism improves regulation performance while maintaining relatively simple circuit topology, as it reuses existing circuit elements rather than adding completely new components.
Solution Approach 2:
The common mode feedback part serves multiple functions: it generates the feedback signal for regulation and simultaneously acts as part of the control mechanism itself. By making the feedback part multi-functional, the patent reduces the need for separate dedicated components, thereby improving regulation ability without proportionally increasing device complexity.
3Stability of the object's composition
If the transistor ability is increased to compensate for fluctuations, then the amplification rate stability improves, but the circuit requires larger transistors which increases area
Solution Approach 1:
The feedback mechanism compensates for transistor ability fluctuations by continuously adjusting the current source based on common mode voltage deviations. When transistor characteristics vary due to temperature or aging, the feedback loop detects the resulting voltage changes and adjusts the operating point accordingly, maintaining amplification rate stability without requiring oversized transistors. This dynamic compensation resolves the contradiction between stability and size.
Solution Approach 2:
The patent introduces dynamic adjustment capability through the feedback loop, allowing the circuit to adapt to changing conditions in real-time. Rather than using statically oversized transistors to cover all possible fluctuation scenarios, the system dynamically adjusts its operating parameters to maintain stability. This dynamic approach achieves the same stability with smaller, more efficient transistors.
Data Source
AI summary
An amplifier includes a signal amplification part that outputs an output signal obtained by amplifying an input signal and a common mode voltage VCM of the output signal, and a common mode feedback part that outputs a signal according to a difference between the common mode voltage VCM and a reference potential Vref as a regulation signal SREG. The regulation signal SREG from the common mode feedback part is fed back to a current source of the signal amplification part and a current source of the common mode feedback part.