Buffered Current Mirror Circuit With Reduced Offset Sensitivity
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Solution Overview
Problem
Current mirrors face challenges in achieving high linearity and wide signal bandwidth, as linearity is often traded off against bandwidth, and existing solutions struggle with stability issues and buffer offset sensitivity at high operating frequencies.
Innovation Solution
Incorporating buffers and additional resistors on the master and slave sides of current mirror circuits, which helps stabilize the circuit, reduces sensitivity to buffer offsets, and improves bandwidth and linearity by degenerating the impact of parasitic capacitances and buffer non-idealities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If buffers are added to stabilize the current mirror circuit, then stability improves, but sensitivity to buffer offsets increases
Solution Approach 1:
The patent introduces an intermediary component (the buffer amplifier) between the master and slave current mirror circuits. This buffer acts as a mediator that isolates the master circuit from the slave circuit, preventing direct interaction and stabilizing the overall circuit operation while managing the buffer offset through proper circuit design
2Measurement precision
If linearity is improved in current mirrors, then signal accuracy increases, but bandwidth decreases
Solution Approach 1:
The patent divides the current mirror circuit into separate master and slave portions with independent biasing and buffering. This segmentation allows each portion to be optimized independently - the master portion for linearity and the slave portion for bandwidth, thereby resolving the traditional linearity-bandwidth tradeoff
3Speed
If buffers are used to improve bandwidth, then signal frequency range increases, but circuit stability deteriorates
Solution Approach 1:
The patent employs feedback mechanisms within the buffer amplifier design and circuit configuration to maintain stability across wide frequency ranges. The feedback loop compensates for phase shifts and gain variations that occur at high frequencies, allowing the buffer to extend bandwidth without sacrificing circuit stability
Data Source
AI summary
An example current mirror arrangement includes a first portion and a second portion, each of which includes a current mirror having transistors Q1 and Q2, a buffer amplifier that has an input coupled to a base/gate terminal of Q1 and an output coupled to a base/gate terminal of Q2, a master resistor coupled to an emitter/source terminal of Q1, and a slave resistor coupled to an emitter/source terminal of Q2. Furthermore, the slave resistor of the first portion is coupled to the slave resistor of the second portion. Providing additional resistors on master and slave sides of a current mirror arrangement may advantageously allow benefiting from the use of buffers outside of a feedback loop of a current mirror while reducing the sensitivity of the current mirror arrangement to buffer offsets.