Cascode Amplifier Isolation via Intermediate-Node Shunt Grounding
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Solution Overview
Problem
Wireless communication devices face performance degradation due to signal leakage when amplifiers are disabled, leading to poor isolation between gain transistors and other circuits, which affects data reception and transmission quality.
Innovation Solution
The implementation of cascode circuits with a shunt path to circuit ground in amplifiers, which includes multiple cascode transistors in series for signal passing and a shunt transistor to provide improved isolation when the amplifier is disabled, using a combination of bias voltages and control signals to enable or disable the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If amplifiers are disabled to save power, then energy consumption is reduced, but signal leakage occurs causing poor isolation between circuits
Solution Approach 1:
A shunt transistor is introduced as an intermediary component between the amplifier output and circuit ground. When the amplifier is disabled, the shunt transistor activates to provide a controlled path to ground, preventing signal leakage while maintaining energy savings. This mediator resolves the contradiction by actively managing the isolation without requiring full amplifier operation.
2Adaptability or versatility
If multiple amplifiers are used for different purposes, then functional versatility is improved, but isolation between amplifier outputs deteriorates
Solution Approach 1:
Individual shunt transistors are placed at each amplifier output as intermediary isolation components. Each shunt transistor can be independently controlled to ground, providing dedicated isolation paths that prevent signal leakage between multiple amplifiers while allowing each to maintain its specific function.
Solution Approach 2:
The isolation mechanism is segmented into independent shunt transistors for each amplifier output. This segmentation allows each amplifier to be independently controlled and isolated, preventing signal leakage between different functional blocks while maintaining the versatility of having multiple amplifiers available.
Data Source
AI summary
Amplifiers with improved isolation are disclosed. In an exemplary design, an apparatus (e.g., a wireless device, an integrated circuit, etc.) includes an amplifier having a gain transistor, first and second cascode transistors, and a shunt transistor. The gain transistor receives an input signal and provides an amplified signal. The first cascode transistor is coupled between the gain transistor and an intermediate node and receives the amplified signal. The second cascode transistor is coupled between the intermediate node and an output node and provides an output signal. The shunt transistor is coupled between the intermediate node and circuit ground. The first and second cascode transistors are enabled to provide the output signal. The shunt transistor is (i) disabled when the cascode transistors are enabled and (ii) enabled to short the intermediate node to circuit ground when the cascode transistors are disabled.