Variable Gain Amplifier Circuit With Fixed Phase Compensation
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Solution Overview
Problem
Conventional variable gain circuits require multiple phase compensation capacities to maintain stability as gain is decreased, leading to increased chip area and production costs in integrated circuits and complexity in discrete circuits.
Innovation Solution
A variable gain circuit configuration where the gain and transconductance value of the precedent stage amplifier circuit are set in conjunction with each other, allowing for phase compensation without multiple phase compensation capacities, using a fixed capacitative element and adjusting the number of active amplifiers or switch circuits based on the set gain value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple phase compensation capacities are provided to maintain circuit stability as gain is decreased, then circuit stability is improved, but chip area and production costs increase
Solution Approach 1:
The patent changes the parameter of transconductance value in conjunction with gain value to maintain circuit stability. By coordinating the adjustment of transconductance value with gain value, the patent achieves stability maintenance without requiring multiple phase compensation capacities, thus reducing chip area while preserving reliability.
2Reliability
If multiple phase compensation capacities are provided to maintain circuit stability as gain is decreased, then circuit stability is improved, but production costs increase
Solution Approach 1:
The patent employs parameter coordination between transconductance value and gain value to maintain circuit stability. This approach eliminates the need for multiple phase compensation capacities, thereby reducing component count and production costs while maintaining the required circuit stability across different gain settings.
3Device complexity
If the number of active amplifiers is adjusted based on gain value, then circuit complexity is reduced, but maintaining stability becomes more difficult
Solution Approach 1:
The patent coordinates the transconductance value parameter with the gain value to maintain stability when adjusting the number of active amplifiers. This parameter coordination ensures that even with reduced circuit complexity from using fewer amplifiers, the circuit stability is preserved through the coupled adjustment of transconductance and gain parameters.
Data Source
AI summary
Provided is a variable gain circuit in which it is not necessary to provide a plurality of phase compensation capacities while stability of a circuit is maintained regardless of a set variable gain. A variable gain circuit comprises a precedent stage amplifier circuit for amplifying an external input signal, a subsequent stage amplifier circuit for amplifying an output signal of the precedent stage amplifier circuit, a phase compensation circuit having a fixed capacitative element and connected between an output terminal and an input terminal of the subsequent stage amplifier circuit, and a gain setting circuit adapted to be capable of setting a gain value of the whole of the precedent stage amplifier circuit and the subsequent stage amplifier circuit to a plurality of values, wherein one of the gain value and a transconductance value of the precedent stage amplifier circuit can be set in conjunction with the other.