Push-Pull Amplifier Bias Calibration for Even-Order Distortion
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Solution Overview
Problem
Signal processing arrangements with complementary transistors in CMOS technology face challenges in achieving low even-order distortion while maintaining stability and performance aspects like sensitivity and signal-to-noise ratio, especially in radiofrequency applications.
Innovation Solution
A controllable biasing circuit adjusts the quiescent operating point of the amplifier stages based on even-order distortion measurements, compensating for nominal differences in transistor characteristics due to design and manufacturing tolerances, using a feedback circuit and controllable current sources to reduce distortion without compromising stability or performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If complementary transistors are formed by different process steps in CMOS technology, then manufacturing complexity is reduced and integration is improved, but even-order distortion increases due to characteristic mismatches
Solution Approach 1:
The patent implements a feedback mechanism where the output signal is fed back through a feedback network to the input, creating a closed-loop system that automatically compensates for even-order distortion caused by transistor mismatches. The feedback signal counteracts the distortion components, reducing their impact on the overall output.
Solution Approach 2:
The patent employs dynamic parameter adjustment by varying the operating point of the amplifier stages through controllable biasing circuits. By changing bias conditions, the transconductance and other critical parameters of the complementary transistors are adjusted to minimize even-order distortion while maintaining stable operation.
2Object-generated harmful factors
If distortion reduction measures are applied to improve linearity, then even-order distortion is reduced, but stability and performance aspects like sensitivity and signal-to-noise ratio may be compromised
Solution Approach 1:
The patent employs dynamic biasing circuits that continuously adjust the operating conditions of the amplifier stages based on real-time signal characteristics. This dynamic adaptation allows the system to maintain optimal linearity and stability across varying input conditions, preventing the trade-off between distortion reduction and stability.
Solution Approach 2:
The feedback mechanism monitors output distortion and automatically adjusts system parameters to maintain stability while reducing even-order distortion. The feedback loop ensures that stability margins are preserved even as linearity improvements are implemented.
3Adaptability or versatility
If complementary transistors are designed with nominally different characteristics to meet digital circuit requirements, then integration with digital circuits is improved, but even-order distortion increases due to characteristic differences
Solution Approach 1:
The patent uses parameter transformation techniques where the inherent characteristic differences between complementary transistors are exploited to achieve both digital circuit compatibility and distortion reduction. By carefully selecting and adjusting operating parameters, the system converts the nominal differences into beneficial effects that reduce even-order distortion.
Data Source
AI summary
A signal processing arrangement comprises an amplifier (AMP V1) that includes a stage with complementary transistors (MP3, MN3) of opposite conductivity type arranged in series between two supply lines (+, −). A controllable biasing circuit (CCS) is provided for changing a quiescent operating point of the stage as a function of a control signal (CS). A control arrangement measures an even order 5 distortion of the amplifier (AMP V1) and adjusts the control signal (CS) so that the even order distortion is below a critical level.