Differential Operational Amplifier Current Control
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Solution Overview
Problem
Differential operational amplifiers face issues with increased distortion rate and power consumption due to large gate capacities of N-MOSFETs, which lead to fluctuations in common-mode voltage and increased current change amounts when input voltages have high amplitudes.
Innovation Solution
A differential operational amplifier design that includes a variable current generation circuit and a constant current generation circuit, where the current driving capability of the variable current generation circuit is smaller than that of the constant current generation circuit, to control the intermediate voltage to a predetermined reference voltage, reducing current change amounts and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gate capacities of N-MOSFETs are increased to reduce 1/f noise, then noise resistance is improved, but power consumption increases and distortion rate deteriorates when input voltages have large amplitudes
Solution Approach 1:
The patent divides the single large-capacity N-MOSFET into multiple smaller N-MOSFETs connected in parallel. This segmentation maintains the total gate capacity needed for noise reduction while allowing better current distribution and reduced power consumption. Each smaller transistor operates more efficiently, reducing overall power consumption while maintaining the noise filtering benefits of large total gate capacity.
Solution Approach 2:
The patent applies different capacities to different N-MOSFETs within the parallel configuration. By using N-MOSFETs with different individual capacities rather than identical ones, the system optimizes local characteristics to balance noise reduction requirements with power consumption constraints, allowing some transistors to contribute more to noise filtering while others contribute less to power draw.
2Object-affected harmful factors
If the gate capacities of N-MOSFETs are increased to reduce 1/f noise, then noise resistance is improved, but distortion rate deteriorates when input voltages have large amplitudes
Solution Approach 1:
The patent segments the large gate capacity into multiple smaller N-MOSFETs in parallel, which reduces the distortion rate under large input voltage conditions. The segmented configuration prevents any single transistor from operating in a high-distortion region, thereby maintaining manufacturing precision and signal fidelity even when noise reduction through large total gate capacity is required.
Solution Approach 2:
By assigning different capacities to different N-MOSFETs in the parallel configuration, the patent optimizes local transistor characteristics to minimize distortion. This local quality variation ensures that the overall system maintains low distortion rates while achieving the noise reduction benefits of large total gate capacity.
3Stability of the object's composition
If the current amount is increased in the common-mode feedback circuit to operate steadily, then control stability is improved, but power consumption increases
Solution Approach 1:
The patent introduces a variable current generation circuit that dynamically adjusts the current supplied to the common-mode feedback circuit based on operating conditions. This dynamic current adjustment maintains control stability when needed while reducing power consumption during normal operation, eliminating the need for continuously high current operation.
Solution Approach 2:
The patent changes the current parameter in the common-mode feedback circuit from a fixed high value to a variable value that adapts to operational requirements. By using a variable current generation circuit, the system can maintain control stability through increased current when necessary while consuming less power during standard operation, thus resolving the contradiction between stability and power consumption.
Data Source
AI summary
Disclosed is a differential operational amplifier that outputs first and second output voltages corresponding to first and second input voltages, the amplifier comprising a differential circuit that operates depending on the first and second input voltages; a control voltage generation circuit that generates a control voltage for making an intermediate voltage of the first and second output voltages become a predetermined reference voltage; a variable current generation circuit that is connected serially to the differential circuit to generate a variable current corresponding to the control voltage; and a constant current generation circuit that is connected in parallel with the variable current generation circuit to generate a constant current, control being performed with the variable current and the constant current such that the intermediate voltage turns to the reference voltage.