Transistor Gain Control Circuit With Unidirectional Noise Reduction
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Solution Overview
Problem
Conventional gain control systems in amplifiers face challenges in efficiently managing gain while minimizing noise, particularly when cross-coupling is necessary for gain control, leading to noise penalties and reduced linearity.
Innovation Solution
The implementation of gain control systems, such as the cross-coupled common-gate stage and alternative configurations like the gain control system 500, which use transistors and current steering signals to control gain reduction without cross-coupling, thereby minimizing noise and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cross-coupled gain control is implemented in the amplifier, then gain control capability is improved, but noise performance deteriorates due to noise penalties
Solution Approach 1:
The patent extracts the harmful cross-coupling feedback path from the gain control system. By using a unidirectional gain control architecture where the control signal flows only from the control input to the amplifier stage without feedback coupling, the design eliminates the noise penalties associated with conventional cross-coupled configurations while preserving gain control functionality.
2Measurement precision
If cross-coupled gain control is used, then gain management precision is improved, but linearity deteriorates
Solution Approach 1:
The patent removes the cross-coupling feedback path that causes non-linearity in conventional gain control systems. By implementing a unidirectional control architecture, the system achieves precise gain management through direct control signaling without the linearity degradation caused by feedback coupling effects.
3Adaptability or versatility
If conventional gain control systems are implemented, then gain control is achieved, but output noise increases due to noise penalties
Solution Approach 1:
The patent extracts and eliminates the feedback coupling path that generates noise penalties in conventional gain control systems. The unidirectional gain control architecture allows gain control functionality to be maintained while preventing the generation of excess output noise through direct control signaling without feedback loops.
Data Source
AI summary
A gain control system may include an input terminal that receives an input signal. The gain control system may include a first transistor having a source connected with the input terminal and a drain connected with an output terminal. The gain control system may include a second transistor having a gate connected with the input terminal and the source of the first transistor. The second transistor may have a drain connected with the output terminal. The second transistor may generate a reduction signal. The output terminal may output an output signal based on the input signal and the reduction signal.