Asymmetric Operational Amplifier for Stable Reference Voltages
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Solution Overview
Problem
Existing amplifier circuits in electronic devices face challenges in generating reference voltages that are invariant to power supply voltage levels and temperature changes, leading to unwanted variations due to differential noise caused by different time constants in circuit nodes, which can be partially remedied by adding capacitors but results in increased circuit size and limited effectiveness over process, power supply, and temperature variations.
Innovation Solution
The proposed solution involves an asymmetric amplifier circuit with input-stage and output-stage circuits, where the input-stage circuit has terminals with different input impedances based on distinct time constants, and the output-stage circuit asymmetrically combines amplified signals to generate an output signal, using a differential transistor pair and current-mirror circuit with transistors of varying physical characteristics to adjust time constants without adding capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If capacitors are added to circuit nodes to adjust time constants, then differential noise is reduced, but circuit size increases
Solution Approach 1:
The patent applies asymmetry by configuring the first and second input terminals with different input impedances. Specifically, the first input terminal has a first input impedance while the second input terminal has a second input impedance that is different from the first. This asymmetric impedance configuration creates different time constants at each input node, which compensates for differential noise without requiring additional capacitors, thereby reducing circuit size while maintaining noise reduction effectiveness.
2Device complexity
If symmetric amplifier circuits are used, then circuit design is simplified, but reference voltage becomes sensitive to power supply variations and temperature changes
Solution Approach 1:
The patent employs asymmetry in the input stage by providing different input impedances at the first and second input terminals. This asymmetric configuration creates unequal time constants that compensate for process, power supply, and temperature variations, thereby stabilizing the reference voltage output. The output stage then symmetrically combines the amplified signals from both inputs, maintaining design simplicity while achieving improved reliability through the asymmetric input configuration.
3Object-affected harmful factors
If input terminals have different input impedances, then time constants are adjusted to reduce differential noise, but circuit symmetry is broken
Solution Approach 1:
The patent deliberately introduces asymmetry at the input terminals by configuring different input impedances for the first and second inputs. This asymmetric impedance configuration creates different time constants that effectively compensate for differential noise. The output stage then restores symmetry by combining the amplified signals in a balanced manner, achieving both noise reduction and signal integrity.
Data Source
AI summary
An asymmetric amplifier circuit is disclosed. The amplifier circuit includes an input-stage circuit and an output-stage circuit. The input stage circuit can include a first terminal with a first input impedance and a second terminal with a second input impedance different than the first input impedance. The input-stage circuit may be configured to receive a first input signal on the first input terminal, receive a second input signal on the second input terminal, and generate a first amplified signal and a second amplified signal using the first input signal and the second input signal. The output-stage circuit may be configured to asymmetrically combine the first amplified signal and the second amplified signal to generate an output signal.