Non-inverting Amplifier Offset Control for 0 V Output
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Solution Overview
Problem
Analog circuits in optical disc systems face challenges in finely adjusting laser power due to the inability to output a voltage of 0 V and provide linearity near 0 V, making it difficult to control laser power effectively.
Innovation Solution
A non-inverting amplifier is designed with an operational amplifier, input resistor, feedback resistor, and a current digital-to-analog converter to control offset voltage, allowing for the output of a voltage of substantially 0 V by supplying a control current to the control node, which is adjustable through a series of current sources and switches controlled by decoded digital values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional analog circuits are used for voltage output, then the circuit structure is simple, but the circuit cannot output a voltage of 0 V and lacks linearity near 0 V
Solution Approach 1:
The patent introduces a control node as an intermediary element between the operational amplifier and the output. This control node receives control current from a current digital-to-analog converter, which adjusts the offset voltage at the control node. By controlling the voltage at this intermediary control node, the operational amplifier can output precisely controlled voltages including 0 V, resolving the contradiction between output precision and circuit complexity.
2Measurement precision
If offset voltage control is added to enable 0 V output, then voltage output precision is improved, but the circuit complexity increases due to additional components
Solution Approach 1:
The patent changes the operating parameters of the operational amplifier by introducing a controllable offset voltage at the control node. The current digital-to-analog converter adjusts the control current to set the control node voltage to specific values, enabling the amplifier to output 0 V or other precise voltage levels. This parameter change approach allows precise offset control while keeping the additional circuitry relatively simple.
3Ease of operation
If conventional analog circuits are used, then the circuit is easy to operate, but fine adjustment of laser power is difficult due to inability to provide linearity near 0 V
Solution Approach 1:
The patent implements a feedback mechanism where the control node voltage is adjusted based on digital control signals that correspond to desired laser power levels. The current digital-to-analog converter translates digital values into precise control currents, which adjust the control node voltage to maintain linearity near 0 V output. This feedback-controlled approach enables both ease of operation through digital control and precise laser power adjustment.
Data Source
AI summary
A non-inverting amplifier includes an operational amplifier, an input resistor, and a feedback resistor. The operational amplifier amplifies and outputs a difference between an input voltage and a voltage of a control node. The input resistor is connected between a reference voltage port and the control node. The feedback resistor is connected to an output port of the operational amplifier and the control node. The non-inverting amplifier supplies a control current to the control node for controlling an offset voltage of the output port.