Variable Negative-Resistance Circuit for Gain Slope Suppression
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Solution Overview
Problem
Conventional distributed amplifiers experience a gain slope due to increasing input capacitance, leading to deteriorated frequency characteristics and output waveforms in high-speed communication systems, and existing solutions like the Capacitive Source Degeneration circuit can vary in characteristics, affecting yield.
Innovation Solution
Incorporating an oscillation transistor and a negative resistance change circuit with variable resistor and capacitor circuits to adjust the input capacitance and negative resistance, allowing for compensation of manufacturing variations and suppression of the gain slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the input capacitance of the input transistor is increased, then the amplifier gain is improved, but the frequency characteristic deteriorates due to gain slope
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the input capacitance value through a variable capacitor circuit. The capacitor value is changed based on the operating frequency to optimize the balance between amplifier gain and frequency characteristic, thereby suppressing gain slope while maintaining high gain performance.
Solution Approach 2:
The patent implements dynamics by making the input capacitance adjustable rather than fixed. A variable capacitor circuit is introduced that can change the capacitance value in response to frequency changes, allowing the amplifier to adapt its characteristics dynamically across different operating conditions to maintain optimal performance.
2Reliability
If the input capacitance is reduced to suppress gain slope, then the frequency characteristic is improved, but the amplifier gain decreases
Solution Approach 1:
The patent resolves this contradiction by making the capacitance value dynamic rather than static. The variable capacitor circuit allows the system to switch between different capacitance values depending on the operating frequency, thereby achieving both flat frequency response and high gain performance across different operating conditions.
Solution Approach 2:
The patent changes the parameter of input capacitance from a fixed value to a variable value that can be adjusted based on frequency requirements. This parameter change enables the system to optimize both frequency characteristic and amplifier gain by selecting appropriate capacitance values for different operating scenarios.
3Ease of manufacture
If fixed capacitor and resistor values are used, then the circuit is simple to manufacture, but manufacturing variations cause characteristic changes and reduce yield
Solution Approach 1:
The patent introduces dynamics by replacing fixed passive components with active variable components. The variable capacitor and resistor circuits allow post-manufacturing adjustment of component values, compensating for manufacturing variations and ensuring consistent performance across production batches, thereby improving yield without significantly complicating the manufacturing process.
Solution Approach 2:
The patent implements self-service by enabling the circuit to self-adjust its characteristics through variable components. The ability to tune capacitor and resistor values allows the manufactured circuit to self-correct for variations, ensuring that each unit meets performance specifications without requiring precise manufacturing control.
Data Source
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Figure 3A~3B
AI summary
An analog circuit is provided, comprising: an oscillation transistor; and a negative resistance change circuit changing negative resistance for said oscillation transistor, wherein said negative resistance change circuit comprises a variable resistor circuit connected to a source of said oscillation transistor.