Complementary Cascode Amplifier With Dynamic Bias for Linearity
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Solution Overview
Problem
Conventional common-source amplifiers face issues of ground bounce and source degeneration due to nonzero resistance in the connection between the source and ground node, and dynamic bias schemes used in conventional amplifiers are not applicable to complementary amplifiers.
Innovation Solution
A complementary amplifier design using a transformer to transform input signals into bias voltages, N-type and P-type dynamic bias circuits to detect peaks and valleys, and N-type and P-type cascode amplifiers sharing a common source node, with bias voltages adjusted dynamically to maintain power efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional common-source amplifier is biased in a deeper class-A region with higher quiescent bias current, then linearity is improved, but power efficiency deteriorates
Solution Approach 1:
The patent implements dynamic bias adjustment where the bias condition is automatically modified in response to input signal characteristics. The amplifier transitions between different bias states (class-A to class-AB/class-C) based on signal amplitude, achieving both high linearity for large signals and high power efficiency for small signals through time-varying operating conditions
2Device complexity
If a conventional common-source amplifier uses a physical connection between source and ground node, then circuit simplicity is maintained, but ground bounce and source degeneration occur due to nonzero resistance
Solution Approach 1:
The patent introduces a virtual ground node created through feedback mechanisms and circuit topology transformation. This virtual intermediary eliminates the direct physical connection between source and ground, thereby removing the harmful resistance effects while maintaining circuit functionality and simplicity through clever topological design
3Reliability
If a complementary amplifier uses both NMOST and PMOST in a hybrid differential pair, then ground bounce and source degeneration are mitigated, but dynamic bias scheme becomes inapplicable
Solution Approach 1:
The patent divides the complementary amplifier into separate N-type and P-type cascode amplifier paths, each with its own bias control mechanism. This segmentation allows independent bias adjustment for each transistor type, making dynamic bias schemes applicable again while preserving the benefits of the complementary structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively mitigates ground bounce and source degeneration, ensuring power efficiency and linearity by dynamically adjusting bias conditions based on input signal amplitude, while maintaining high voltage gain and reverse isolation.
Implementation Method 1
a transformer configured to transform an input signal received from a primary coil into a first transformed signal of a first bias voltage and a second transformed signal of a second bias voltage via a first secondary coil and a secondary coil, respectively
Data Source
AI summary
A method operates by receiving an input signal; transforming the input signal into a first transformed signal of a common-mode voltage equal to a first bias voltage; transforming the input signal into a second transformed signal of a common-mode voltage equal to a second bias voltage; detecting a peak of the first transformed signal and making the first bias voltage equal to a sum of a first DC (direct current) voltage and a first dynamic voltage; detecting a valley of the second transformed signal and making the second bias voltage equal to a sum of a second DC voltage and a second dynamic voltage; amplifying the first transformed signal into a first output signal across a first load using a N-type cascode amplifier; and amplifying the second transformed signal into a second output signal across a second load using a P-type cascode amplifier.