Differential Amplifier Current Combining for Wider Input Range
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Solution Overview
Problem
Existing differential amplifier circuits face challenges in extending the range of input voltage, output voltage, and operating currents due to limitations in the subtractive combination of currents from Nch-type and Pch-type MOSFETs, leading to potential circuit failure and increased power-supply current consumption.
Innovation Solution
The proposed differential amplifier circuit combines the output currents of first and second differential amplifiers with differing polarities additively, using current mirrors to ensure non-zero current values and normal operation across a wider range of input voltages, employing diode-connected transistors as load elements and current combining circuits to maintain circuit functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If subtractive combination of currents from Nch-type and Pch-type MOSFETs is used, then the circuit can operate with conventional differential amplifier configuration, but the range of input voltage and operating currents is limited and circuit failure may occur
Solution Approach 1:
The patent merges the output currents of first and second differential amplifiers with different polarities through additive combination instead of subtractive combination. This is achieved by connecting the output pair of each differential amplifier to current combining circuits that sum the currents, thereby extending the input voltage range and preventing circuit failure that occurs with conventional subtractive combination.
2Device complexity
If subtractive combination of currents is used in differential amplifier, then the conventional circuit configuration can be maintained, but power-supply current consumption increases
Solution Approach 1:
The patent combines multiple differential amplifiers with different polarities using additive current combination, which efficiently utilizes the current outputs to extend voltage range operation. This approach reduces redundant current consumption compared to conventional subtractive combination while maintaining practical circuit complexity through systematic current merging.
3Use of energy by moving object
If the ratio of threshold-value voltage to input voltage range increases due to lowered power-supply voltage, then MOSFET operation becomes more constrained, but circuit performance essentially declines
Solution Approach 1:
The patent segments the differential amplifier function into multiple differential amplifiers with different polarities (Nch-type and Pch-type MOSFETs). Each segment operates effectively in different voltage ranges, and their outputs are combined additively. This segmentation allows the overall circuit to maintain high performance across a wider input voltage range even when power-supply voltage is reduced, overcoming the threshold voltage constraints of individual MOSFETs.
Data Source
AI summary
Disclosed is a differential amplifier circuit that comprises: a first differential pair of a first conductivity type having an input pair connected to respective input terminals and an output pair connected to a load-element pair; a second differential pair of a second conductivity type having an input pair connected to the respective input terminals and an output pair connected to a load-element pair; a first output transistor connected between a first power supply and an output terminal and having a control terminal connected to a first output of the first differential pair; and a second output transistor connected between a second power supply and the output terminal and having a control terminal connected to a first output of the second differential pair. A current having a value that is the result of adding a current, which is the result of reflecting a current of the second output of the second differential pair by a current mirror, to a current of the first output of the first differential pair, is passed into the load element connected to the first output of the first differential pair. A current having a value that is the result of adding a current, which is the result of reflecting a current of the second output of the first differential pair by a current mirror, to a current of the first output of the second differential pair, is passed into the load element connected to the first output of the second differential pair.