Amplifier Bias Circuit With Feedback-Stabilized High PSRR
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Solution Overview
Problem
Conventional amplifiers face challenges in achieving high power-supply rejection ratio (PSRR) and stability due to voltage drop issues, especially when using negative charge pumps, which can lead to inefficiency and high fabrication costs, particularly in low voltage low cost semiconductor processes.
Innovation Solution
The proposed amplifier circuit combines a low dropout regulator and a negative charge pump to generate stable output voltages, with a closed-loop feedback mechanism using metal-oxide semiconductor field effect transistors (MOSFETs) to regulate voltages independently of input voltage changes, ensuring high PSRR and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a negative charge pump is used to bias the output end to system ground, then the amplifier can operate with proper biasing, but the voltage drop on the amplifier becomes too large
Solution Approach 1:
The patent introduces an intermediary circuit between the negative charge pump and the amplifier that actively regulates the voltage. This intermediary uses feedback control to maintain a stable voltage level, preventing the excessive voltage drop that would otherwise occur when using a simple negative charge pump configuration.
Solution Approach 2:
The patent implements a feedback mechanism where the output voltage is monitored and used to adjust the operation of the negative charge pump. This feedback loop ensures that the voltage remains within acceptable ranges, preventing the voltage drop from becoming too large while still enabling proper biasing.
2Ease of operation
If conventional charge pump is used, then the amplifier can be biased, but the output voltage is affected by input voltage changes resulting in poor PSRR
Solution Approach 1:
The patent employs a feedback control system that continuously monitors the output voltage and adjusts the charge pump operation accordingly. This feedback mechanism decouples the output voltage from input voltage variations, ensuring stable operation and high power supply rejection ratio (PSRR).
Solution Approach 2:
The patent dynamically adjusts operating parameters of the charge pump based on feedback signals. By changing control voltages and switching timings in response to output conditions, the system maintains stable output voltage despite input voltage fluctuations, achieving high PSRR.
3Ease of operation
If negative charge pump is used to enable proper biasing, then the amplifier can operate, but the fabrication cost increases
Solution Approach 1:
The patent optimizes the operating parameters of the negative charge pump and associated circuits to enable fabrication in low-voltage, low-cost semiconductor processes. By adjusting voltage levels and current characteristics, the design achieves proper biasing capability while being compatible with cost-effective manufacturing technologies.
Data Source
AI summary
The embodiments of the present invention disclose a high power-supply rejection ratio (PSRR) amplifier circuit. The amplifier circuit comprises a low dropout regulator, a negative charge pump and an amplifier. The output voltages of the negative charge pump and the low dropout regulators don't track the change of input voltage. Therefore the amplifier circuit has high PSRR.