Differential Amplifier Feedback Circuit for Low Output Voltage Error
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cascode differential amplifiers suffer from output voltage errors due to non-ideal semiconductor process variations, causing shifting in the input/output voltage conversion curve, which affects the accuracy of circuits like voltage detectors and comparators.
Innovation Solution
A differential amplifier design that includes a differential input circuit, current source circuits, a current-mirror circuit, and an impedance circuit, which adjusts currents based on input voltages and reference voltages to reduce the shifting of the conversion curve, utilizing bilaterally symmetrical dimensions and resistors to minimize output voltage errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cascode differential amplifier is used to achieve wider input and output ranges, then the input and output ranges are improved, but the conversion curve shifts due to non-ideal characteristics causing output voltage errors
Solution Approach 1:
The patent introduces a feedback mechanism where the output voltage is fed back through a feedback transistor (M12) to the gate of the first cascode transistor (M1). This feedback loop automatically adjusts the operating point to compensate for process variations and non-ideal characteristics, thereby reducing output voltage errors while maintaining the wide input/output range capability of the cascode configuration
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the gate voltages of the cascode transistors through the feedback mechanism. By changing the operating parameters (voltages and currents) in response to output conditions, the circuit compensates for process variations and maintains accurate conversion characteristics across the wide operating range
2Device complexity
If standard cascode differential amplifier configuration is used, then circuit simplicity is maintained, but conversion curve shifting occurs due to semiconductor process variations
Solution Approach 1:
The feedback transistor (M12) creates a self-correcting mechanism that monitors the output voltage and adjusts the gate voltage of M1 accordingly. This feedback loop compensates for process variations without requiring complex external calibration circuits, maintaining relatively simple circuit architecture while significantly improving conversion curve stability and reducing output voltage errors
Data Source
AI summary
A differential amplifier is provided. The differential amplifier includes: a differential input circuit, adjusting a second current and a third current flowing into the differential input circuit according to a first input voltage, a second input voltage, and a first current; a first current source circuit, generating the first current according to a first reference voltage; a current-mirror circuit, generating a fifth current according to a fourth current; a second current source circuit, generating a sixth current and a seventh current according to a second reference voltage; and an impedance circuit, coupled to the current-mirror circuit and a ground terminal, the differential amplifier having a low output voltage error.