Grounded-Gate Amplifier Circuit for Broadband 50Ω Matching
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Solution Overview
Problem
Existing amplifier circuits face challenges in achieving high amplification over a broad frequency range while maintaining input and output impedances at a matching value of 50Ω, particularly in high-frequency applications, as they tend to experience gain reduction at frequencies away from the center frequency due to impedance mismatching.
Innovation Solution
The proposed solution involves a two-stage grounded-gate amplifier circuit configuration, where a first inductor is connected between the drain of the first transistor and the source of the second transistor, and a second inductor is connected between the drain of the second transistor and the output port, allowing for the adjustment of mutual conductance and inductance values to maintain 50Ω impedances and increase voltage gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If grounded-source transistors are cascade-connected to increase amplification, then voltage gain is improved, but impedance matching becomes difficult and bandwidth is reduced
Solution Approach 1:
The patent introduces a feedback circuit comprising a feedback resistor and feedback capacitor as an intermediary element between the cascade-connected grounded-gate transistor stages. This feedback circuit mediates the impedance transformation, allowing each transistor stage to operate with optimal gain while the overall circuit achieves 50Ω input and output impedance matching across a broad frequency range.
2Adaptability or versatility
If feedback circuit is added to reduce input and output impedances, then impedance matching is improved, but voltage gain is reduced
Solution Approach 1:
The patent merges the feedback impedance reduction function with the transistor cascade amplification function. By cascade-connecting grounded-gate transistors (which naturally provide low input impedance of 1/gm) and combining this with a feedback circuit, the system achieves both impedance matching and high voltage gain simultaneously, rather than treating them as separate conflicting requirements.
3Adaptability or versatility
If inductors are used in series to match input impedance, then input matching is improved at center frequency, but gain is reduced at frequencies away from center frequency
Solution Approach 1:
The patent replaces the static inductor-based matching approach with a dynamic feedback mechanism. The feedback circuit with resistor and capacitor creates a frequency-dependent impedance transformation that adapts across the bandwidth, maintaining both input matching and high gain at frequencies away from any single center frequency, thereby achieving broadband performance.
Data Source
AI summary
There is provided an amplifier circuit including: a first transistor having a source thereof connected to an input port and having a gate thereof grounded; a second transistor having a gate thereof grounded; a first inductor provided between a drain of the first transistor and a source of the second transistor; and a second inductor provided between a drain of the second transistor and an output port.