Low-Noise Buffer Circuit With Split Current Drive and High PSRR
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Solution Overview
Problem
Conventional operational amplifiers and source followers consume high power, generate significant noise, and occupy large areas due to their complex structure and lack of efficient current drive capabilities.
Innovation Solution
An ultra low power low noise buffer is designed with a source current drive circuit and a sink current drive circuit, incorporating transistors and current sources to enhance current drive capabilities, reducing chip area, power consumption, noise, and output resistance, and improving Power Supply Rejection Ratio (PSRR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional operational amplifier is used, then amplification function is achieved, but power consumption increases and noise increases
Solution Approach 1:
The operational amplifier is divided into two separate stages: a first stage with a first transistor for low-noise amplification and a second stage with a second transistor for power-efficient operation. This segmentation allows each stage to be optimized independently, achieving low noise in the first stage and low power consumption in the second stage, thereby resolving the contradiction between power consumption and noise generation.
2Power
If two-stage amplifier is used, then amplification factor is improved, but device complexity increases
Solution Approach 1:
The feedback network is merged with the two-stage amplifier structure, where the feedback path directly connects the output of the second transistor to the input of the first transistor. This integration simplifies the overall circuit design while maintaining the high amplification factor benefits of the two-stage configuration, reducing device complexity compared to separate amplifier and feedback network implementations.
3Object-generated harmful factors
If conventional source follower is used, then noise is reduced and size is minimized, but driving capability is lost
Solution Approach 1:
The first transistor acts as an intermediary between the input signal and the second transistor. It provides the low-noise signal coupling characteristic of a source follower while also driving the second transistor to maintain driving capability. This intermediary role allows the circuit to benefit from both the noise reduction of a source follower and the driving capability of a powered amplifier stage.
Data Source
AI summary
Provided is an ultra low power low noise buffer and an electronic device. The ultra low power low noise buffer includes: a source current drive circuit; and a sink current drive circuit, the sink current driving circuit includes a first transistor, a second transistor and a first current source connected to each other, and the source current drive circuit includes a second current source, a third transistor, an operational amplifier and a voltage source, the second current source is electrically connected to the first transistor and the third transistor, the third transistor is electrically connected to the first transistor and the operational amplifier, and the operational amplifier is electrically connected to the voltage source, the first transistor, the second transistor and the first current source. The chip area, the power consumption, noise induction, output resistance and total harmonic distortion are reduced, and the power supply rejection ratio is improved.