Widlar Bandgap Voltage Comparator Temperature Stability
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Solution Overview
Problem
Voltage comparator circuits with bandgap reference voltages face challenges in maintaining reliable performance across varying temperatures due to the dependency of their threshold voltages on temperature coefficients, limiting their operational range and accuracy.
Innovation Solution
The comparator apparatus incorporates a Widlar bandgap circuit with specific impedance and transistor configurations, including adjusting impedances, to derive a temperature-independent threshold voltage, allowing for adjustable threshold voltages greater than the bandgap voltage while maintaining temperature independence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a bandgap reference voltage of about 1.25 volts is used in the comparator circuit, then the reference voltage provides temperature independence, but the minimum operating voltage increases to about 1.4 volts, limiting the operational range
Solution Approach 1:
The patent modifies the standard bandgap reference voltage parameter by adding a voltage drop across a resistor in the feedback path. This changes the effective reference voltage from the standard 1.25V to a lower value (e.g., 1.1V), allowing the comparator to operate at lower supply voltages while maintaining temperature independence. The resistor value is specifically chosen to create the desired voltage drop that enables extended operational range.
2Adaptability or versatility
If the threshold voltage is adjusted to extend the operational range, then the adaptability improves, but the temperature independence may be compromised
Solution Approach 1:
The patent employs feedback mechanisms where the output signal is fed back through a resistor to modify the reference voltage. This feedback approach allows the threshold voltage to be adjusted to extend operational range while maintaining temperature independence, as the feedback path compensates for temperature variations in the adjusted voltage levels.
Solution Approach 2:
The patent changes the reference voltage parameter by introducing a voltage drop across a resistor in the feedback path. This modifies the effective reference voltage to a lower value while preserving temperature independence, enabling the comparator to operate reliably across a wider voltage range without sacrificing thermal stability.
Data Source
AI summary
Apparatus to compare an input signal to a threshold level are disclosed. An example circuit described herein includes a Widlar bandgap circuit to receive the input signal, an intermediate stage coupled with the output of the Widlar bandgap circuit, and a final stage coupled with the output of the intermediate stage, the final stage to provide an output based on the input signal and the threshold level.