Shared-Input Operational Amplifier for Parallel Current Integration
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Solution Overview
Problem
Ambient light sensors require multiple current integrators and operational amplifiers to handle simultaneous processing of various light elements, leading to high power consumption and significant area occupation.
Innovation Solution
An operational amplifier and current integrator design that includes an input stage, current mirror, and cascode circuit, allowing concurrent multiple current integrations with reduced power consumption and area, utilizing a shared input stage and multiple output terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple current integrators and operational amplifiers are used to handle multiple photodiode currents simultaneously, then the ambient light sensor can process various light elements (RGB, infrared, dark light) in parallel, but the power consumption increases significantly and the area occupied is considerable
Solution Approach 1:
The patent merges multiple operational amplifiers into a single operational amplifier by sharing the input stage among multiple current integrators. The first input transistor and second input transistors form a shared differential input stage that can handle multiple photodiode currents simultaneously, eliminating the need for separate operational amplifiers for each integrator and reducing overall power consumption
Solution Approach 2:
The shared input stage serves multiple functions by processing signals from multiple photodiodes (RGB, infrared, dark light) through a single operational amplifier. The first input transistor and second input transistors can selectively receive different photodiode currents and route them through the same amplification and integration path, making the circuit multi-functional rather than requiring dedicated circuits for each light element
2Productivity
If multiple current integrators and operational amplifiers are used to handle multiple photodiode currents simultaneously, then the ambient light sensor can process various light elements (RGB, infrared, dark light) in parallel, but the area occupied is considerable
Solution Approach 1:
The patent combines multiple current integrators into a single integrated circuit structure where the input stage, current mirror, and cascode circuit are shared resources. This merging approach reduces the total circuit area by eliminating redundant components that would exist if separate operational amplifiers were used for each integrator
Solution Approach 2:
The current mirror is segmented into multiple independent mirror circuits (first mirror circuit, second mirror circuit, third mirror circuit) that can independently mirror currents from different photodiodes. This segmentation allows parallel processing of multiple light elements while sharing common circuit resources, achieving area efficiency without sacrificing parallel processing capability
3Use of energy by moving object
If a shared input stage with multiple input transistors is used, then power consumption and area are reduced, but the circuit must maintain signal integrity and stability across multiple parallel processing paths
Solution Approach 1:
The current mirror acts as an intermediary between the shared input stage and the integration capacitors. It provides isolated current copying paths for each photodiode signal, ensuring that signals from different photodiodes (RGB, infrared, dark light) are processed independently without interfering with each other, thus maintaining signal integrity while sharing common circuit resources
Solution Approach 2:
The cascode circuit provides feedback stabilization for the current mirror operation. By using cascode transistors in series with the current mirror transistors, the circuit achieves better output impedance and reduced sensitivity to voltage variations, ensuring stable and reliable signal processing across all parallel paths
Data Source
AI summary
An operational amplifier and a current integrator using the same are provided. The operational amplifier includes an input stage, a current mirror, and a cascode circuit. The input stage includes a first input transistor and a plurality of second input transistors. The current mirror includes a first mirror circuit and a plurality of second mirror circuits. The cascode circuit is connected to the current mirror and the input stage, and the cascode circuit includes a first cascode branch and a plurality of second cascode branches. The first cascode branch is connected to the first input transistor and the first mirror circuit. The plurality of second cascode branches are respectively connected to the plurality of second input transistors and respectively connected to the plurality of second mirror circuits. A plurality of output terminals are located between the plurality of second cascode branches and the plurality of second mirror circuits.