Single-Ended to Differential LNA Using Cascode Cascade Topology
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Solution Overview
Problem
Conventional low noise amplifiers with single-ended input to differential-ended output structures face inefficiencies in reducing common mode noise and incur increased noise figure due to the need for baluns, which also raise implementation costs and parasitic effects under high frequencies.
Innovation Solution
A single-ended input to differential-ended output low noise amplifier is implemented using cascode and cascade topology with specific configurations of transistors and impedances, including inductive and capacitive impedances, to achieve phase differences and impedance matching, eliminating the need for baluns and improving signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a balun is added to transform single-ended input to differential-ended output, then differential output capability is achieved, but noise figure increases and cost increases
Solution Approach 1:
The invention extracts and eliminates the balun component from the signal path by directly generating differential outputs from the common-source transistor pair. The differential output capability is achieved through the intrinsic symmetry of the transistor pair and their connection to the current mirror load, without requiring an external balun transformer.
Solution Approach 2:
The invention merges the functions of signal amplification and differential output generation into a single integrated circuit stage. The common-source transistor pair simultaneously provides signal amplification and generates differential outputs, combining multiple functions that would traditionally require separate components.
2Adaptability or versatility
If a balun is added to transform single-ended input to differential-ended output, then differential output capability is achieved, but implementation cost increases
Solution Approach 1:
The invention extracts and eliminates the balun component from the signal path by directly generating differential outputs from the common-source transistor pair. The differential output capability is achieved through the intrinsic symmetry of the transistor pair and their connection to the current mirror load, without requiring an external balun transformer.
Solution Approach 2:
The invention merges the functions of signal amplification and differential output generation into a single integrated circuit stage. The common-source transistor pair simultaneously provides signal amplification and generates differential outputs, combining multiple functions that would traditionally require separate components.
3Device complexity
If conventional single-ended input to single-ended output structure is used, then circuit simplicity is maintained, but common mode noise suppression capability is lost
Solution Approach 1:
The invention utilizes the asymmetric configuration of the common-source transistor pair with respect to the single-ended input, where one transistor processes the input signal while the other provides a complementary output. This asymmetric arrangement enables common mode noise suppression by creating differential outputs that naturally reject common mode interference.
Solution Approach 2:
The invention converts the potential harm of common mode noise into a benefit by using the differential output structure to reject common mode interference. The common mode noise that would normally degrade single-ended output quality is automatically suppressed by the differential configuration, turning a vulnerability into an advantage.
4Object-affected harmful factors
If differential-ended input to differential-ended output structure is used, then common mode noise suppression is improved, but device complexity and parasitic effects increase
Solution Approach 1:
The invention utilizes the asymmetric configuration of the common-source transistor pair with respect to the single-ended input, where one transistor processes the input signal while the other provides a complementary output. This asymmetric arrangement enables common mode noise suppression by creating differential outputs that naturally reject common mode interference.
Solution Approach 2:
The invention converts the potential harm of common mode noise into a benefit by using the differential output structure to reject common mode interference. The common mode noise that would normally degrade single-ended output quality is automatically suppressed by the differential configuration, turning a vulnerability into an advantage.
Data Source
AI summary
A low noise amplifier has the properties of low noise figure and high gain under a high-frequency operation. The low noise amplifier includes a first transistor, a first inductive impedance, a first gate voltage source, a matching circuit, an input, a second inductive impedance, a second transistor, a first capacitive impedance, a second gate voltage source, a third transistor, a third gate voltage source, a second capacitive impedance, a first impedance, a second impedance, a direct current source, a first output, a second output, a first resistor, a second resistor, a third resistor, a first bulk voltage source, a second bulk voltage source, and a third bulk voltage source.