Adjustable Transconductance Amplifier for CMOS Mismatch Compensation
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Solution Overview
Problem
Differential signal processing circuits face performance degradation due to mismatches in discrete components, leading to reduced gain and undesirable hysteresis in transconductance amplifiers, particularly in CMOS manufacturing processes with minimum geometries of 65-nm or below.
Innovation Solution
A transconductance amplifier design with adjustable transconductors, including control ports for adjusting transconductance, allows for individual control of transconductance elements to minimize impedance mismatch, utilizing tri-state inverters and arrays of transconductance elements to optimize differential voltage gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If discrete components are used in differential signal processing circuits, then the circuit can be manufactured with standard CMOS processes, but component mismatch occurs leading to reduced gain and hysteresis
Solution Approach 1:
The patent applies parameter changes by making the transconductance of each transconductor adjustable through control signals. By dynamically tuning the transconductance parameters (gm1, gm2, gm3, gm4) of individual transconductors, the system can compensate for manufacturing mismatches and optimize differential gain, resolving the contradiction between ease of CMOS manufacture and manufacturing precision.
2Device complexity
If fixed transconductance values are used in transconductors, then the circuit design is simpler, but the differential gain cannot be optimized due to component mismatch
Solution Approach 1:
The patent implements dynamics by introducing adjustable transconductance control to each transconductor. The transconductance values are no longer fixed but can be dynamically tuned through control signals applied to the gates of the transistors. This dynamic adjustment capability allows optimization of differential gain while managing the increased design complexity through systematic control mechanisms.
Solution Approach 2:
The patent applies feedback principles by using the adjustable transconductance control to compensate for mismatches. The control signals can be tuned based on the actual performance of each transconductor, creating a feedback mechanism that optimizes the differential gain. This feedback approach improves reliability by allowing real-time compensation for component variations.
3Reliability
If transconductance is made adjustable with control ports, then mismatch compensation and gain optimization are enabled, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the differential amplifier into four separate transconductors (gm1, gm2, gm3, gm4), each with its own independent control port. This segmentation allows individual tuning of each transconductor's transconductance, enabling precise mismatch compensation. The complexity is managed by treating each transconductor as an independent adjustable unit rather than a monolithic block.
Data Source
AI summary
A transconductance amplifier has a pair of input terminals and a pair of output terminals. A first pair of transconductors is connected to the input terminals and the output terminals. A second pair of transconductors has inputs connected to output terminals, and outputs connected to the opposing output terminals. A third pair of transconductors has both its inputs and its outputs connected to the output terminals. One or more of the transconductors have a control port for a control signal to adjust its transconductance. The control signal may switch the transconductance of this or these transconductors between two or more values. One or more of the transconductors in the transconductance amplifier may include a tri-state inverter, which may be enabled or disabled through a control port.