Differential Amplifier Bias Control for Low-Voltage Offset Reduction
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Solution Overview
Problem
Existing reference voltage generating circuits face accuracy issues due to increased dependence on power supply voltage, particularly caused by input offset voltage generated by differential amplifiers, which becomes unstable at lower power supply voltages.
Innovation Solution
A differential amplifier circuit with a bias control mechanism that detects and reduces input offset voltage by controlling the bias current based on potential differences between output signals, ensuring stability across varying power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power supply voltage is lowered to reduce power consumption, then power consumption is reduced, but accuracy of reference voltage output deteriorates due to increased dependence on power supply voltage
Solution Approach 1:
The patent implements a feedback mechanism where the differential amplifier monitors the output reference voltage and adjusts its operation accordingly. The circuit uses the output voltage itself as feedback to compensate for power supply variations, allowing the amplifier to maintain accuracy even at lower power supply voltages by dynamically adjusting its bias and operating point based on actual output conditions
Solution Approach 2:
The patent changes operating parameters of the differential amplifier dynamically. Specifically, it adjusts the bias current and operating point of the amplifier based on the detected output voltage level and power supply conditions. This parameter adaptation allows the circuit to optimize its performance for low-voltage operation while maintaining reference voltage accuracy
2Use of energy by moving object
If power supply voltage is lowered, then power consumption is reduced, but stability of reference voltage deteriorates due to increased dependence on power supply voltage
Solution Approach 1:
The differential amplifier uses feedback from the output reference voltage to detect and compensate for power supply variations. By continuously monitoring the output and adjusting its operation, the circuit maintains stable reference voltage output even when power supply voltage fluctuates at low voltage conditions
Solution Approach 2:
The circuit design incorporates compensation mechanisms that anticipate and counteract the expected deterioration in stability at low voltages. The differential amplifier is designed with built-in compensation for power supply dependence, effectively cushioning against the instability that would normally occur at lower power supply voltages
3Device complexity
If finite gain differential amplifier is used, then device complexity is reduced, but input offset voltage increases causing accuracy deterioration
Solution Approach 1:
The patent uses feedback to detect and compensate for the input offset voltage generated by the finite gain differential amplifier. The circuit monitors the output and adjusts operating conditions to minimize the effect of offset voltage, allowing the use of simple finite gain amplifiers without sacrificing accuracy
Solution Approach 2:
The differential amplifier circuit is designed to self-correct its offset voltage through automatic adjustment of bias conditions. The circuit uses its own output to regulate its operating point, effectively eliminating the need for complex external offset compensation circuits while maintaining high accuracy
Data Source
AI summary
A differential amplifier includes a main differential amplifier circuit that receives a pair of input signals and supplies a pair of output signals based on a difference between the input signals; and a bias control differential amplifier circuit that receives the pair of output signals, controls a control terminal of a current-limiting transistor making up the main differential amplifying circuit based on an offset voltage included in the output signals, and reduces the offset voltage.