Trifferential Amplifier Feedback Circuit for Stable Common-Mode Output
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Solution Overview
Problem
Existing differential amplifiers are inadequate for processing three input voltages to produce three output voltages where the voltage difference between any pair of outputs is proportional to the corresponding input voltage differences, while maintaining a constant average value of the outputs unrelated to the inputs, especially in applications requiring compactness, low power consumption, and fewer components.
Innovation Solution
A trifferential amplifier system with multiple input terminals interconnected through input impedances and a feedback network of summing circuits that combines amplifier outputs in different sets to maintain proportional voltage differences between pairs of outputs and a constant average value, utilizing multiple differential input/output circuits to achieve these objectives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three single-ended amplifiers are used to process three input voltages, then the processing capability is provided, but the output common-mode voltage cannot be maintained constant and unrelated to the input common-mode voltage
Solution Approach 1:
The patent combines three single-ended amplifiers into a single integrated trifferential amplifier circuit that processes three input voltages simultaneously. The merged circuit includes a differential pair with three input terminals and shared current sources, enabling all three signals to be processed while maintaining a constant output common-mode voltage through the shared tail current connection.
Solution Approach 2:
The patent implements feedback mechanisms through the shared current sources and differential pair configuration. The tail current sources provide negative feedback that automatically regulates the output common-mode voltage to remain constant and independent of input common-mode variations, ensuring stable operation across all three output channels.
2Reliability
If conventional differential amplifier configurations are used, then differential signal processing is achieved, but the component count and circuit complexity increase
Solution Approach 1:
The patent merges the functionality of multiple differential amplifier stages into a single integrated circuit. By using a differential pair with three input terminals sharing common current sources and output stages, the design achieves differential signal processing for all three inputs simultaneously without requiring separate amplifier circuits for each signal path.
Solution Approach 2:
The trifferential amplifier circuit performs multiple functions within a single configuration: it processes three differential input signals, maintains constant output common-mode voltage, provides differential to single-ended conversion, and rejects common-mode interference. This multi-functional design eliminates the need for separate circuits for each function.
3Reliability
If additional inverters are added to maintain output common-mode voltage, then the common-mode stability is improved, but the power consumption and chip area increase
Solution Approach 1:
The trifferential amplifier circuit maintains output common-mode voltage stability through its inherent differential pair configuration and shared current sources. The circuit self-regulates the common-mode level through the natural behavior of the differential pair and tail current sources, eliminating the need for additional active components like inverters that would consume extra power.
Solution Approach 2:
The patent extracts and eliminates the need for additional inverter circuits that would be required in conventional designs. By designing the trifferential amplifier with shared current sources and a common differential pair structure, the circuit achieves common-mode stability without the extra components, thereby reducing power consumption and chip area.
4Adaptability or versatility
If multiple separate amplifier circuits are used to handle three inputs and outputs, then the processing function is achieved, but the chip area and component count increase
Solution Approach 1:
The patent merges three separate amplifier processing functions into a single integrated trifferential amplifier circuit. The differential pair with three input terminals and shared current sources processes all three signals simultaneously within one compact circuit block, dramatically reducing the chip area compared to three separate amplifier circuits.
Solution Approach 2:
The single trifferential amplifier circuit performs multiple processing functions: it handles three differential input signals, provides differential to single-ended conversion for all outputs, maintains common-mode voltage stability, and rejects common-mode interference. This multi-functional integration minimizes the required chip area while maintaining full processing capability.
Data Source
AI summary
A multi-fferential amplifier system includes an amplifier having a plurality of amplifier inputs and a plurality of amplifier outputs; a plurality of input terminals for receiving a plurality of inputs and being interconnected with the amplifier inputs through a plurality of input impedances, respectively, and a feedback network including a plurality of summing circuits for combining the plurality of amplifier outputs in a plurality of different sets of groups each group numbering one fewer than the plurality, respectively, and feeding back the sum of each group of amplifier outputs to the remaining amplifier input for maintaining the difference between any group of amplifier outputs proportional to the difference of a corresponding group of inputs at the terminals and maintaining the average value of the amplifier outputs constant and unrelated to the inputs at the terminal. Also disclosed is a multi-fferential amplifier including a plurality of differential input/output circuits responsive to a plurality of input signals and providing a plurality of output signals; each input signal is shared between a different set of differential input/output circuits in a plurality of different sets of groups, each group numbering one fewer than the plurality; each differential input/output circuit receives one input signal at its positive input and the other input signal at its negative input.