Differential Amplifier Feedback Network for High Input Impedance
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Solution Overview
Problem
Conventional amplifier circuits face challenges in reducing the load on previous stages while minimizing noise, as they fail to adequately increase input impedance and reduce electrical currents effectively.
Innovation Solution
The proposed amplifier circuit incorporates a fully-differential operational amplifier with specific impedance elements, including input impedance elements and positive feedback impedance elements, to increase input impedance without increasing the impedance value of the input impedance elements, thereby reducing noise and load on previous stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the impedance value of input impedance elements is increased to reduce load on previous stages, then input impedance is improved, but noise production increases
Solution Approach 1:
The patent introduces positive feedback impedance elements connected between the output terminals and the input impedance elements. This feedback mechanism allows the circuit to maintain high input impedance while controlling noise through the feedback path, resolving the contradiction between high impedance and low noise requirements
Solution Approach 2:
The patent changes the impedance parameters by introducing positive feedback impedance elements with specific impedance values. By carefully selecting and adjusting these impedance parameters, the circuit achieves high input impedance without the noise penalties associated with simply increasing input impedance element values
2Loss of energy
If the impedance value of input impedance elements is increased to reduce electrical currents, then load on previous stages is reduced, but noise production increases
Solution Approach 1:
The positive feedback impedance elements create a feedback path that reduces the electrical currents flowing through the input impedance elements while maintaining low noise. The feedback mechanism allows current reduction without the noise increase that would result from simply increasing input impedance element values
3Power
If additional input impedance elements are added to increase impedance ratio, then voltage gain is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the functions of input impedance elements and feedback elements into a unified configuration. By combining these functions and using shared circuit elements, the patent achieves high voltage gain without proportionally increasing circuit complexity
Data Source
AI summary
An amplifier circuit capable of reducing load of a circuit at the previous stage by providing increased input impedance producing less noises. The amplifier circuit includes a fully-differential operational amplifier composed of an inverting input terminal, a non-inverting input terminal receiving a signal different from a signal to be input to the inverting input terminal, an inverting output terminal with the same polarity of the inverting input terminal, and a non-inverting output terminal with reverse polarity; an input impedance element with one end connected to the inverting input terminal; an input impedance element with one end connected to the non-inverting input terminal; and positive feedback impedance elements, with one end of connected to the other end of the input impedance element and the other end connected to the inverting output terminal or to the non-inverting output terminal.