Reference Voltage Circuit Temperature Stability via Differential Amplifier
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Solution Overview
Problem
Conventional reference voltage circuits exhibit unsuitable temperature characteristics due to a constant temperature gradient, which is not ideal for applications requiring flat temperature stability.
Innovation Solution
A reference voltage circuit utilizing differential amplifier means with depletion transistors having different threshold voltages to generate a reference voltage based on the difference between voltages produced by these transistors, thereby achieving improved temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If depletion transistors with different threshold voltages are used to generate reference voltage based on voltage difference, then temperature characteristics are improved, but device complexity increases
Solution Approach 1:
The reference voltage circuit is divided into multiple constant voltage circuits (first constant voltage circuit with first depletion transistor, second constant voltage circuit with second depletion transistor), each generating voltage with different temperature gradients. This segmentation allows independent optimization of temperature characteristics for each segment while combining them to achieve overall flat temperature response.
Solution Approach 2:
Different depletion transistors are selected with specific local properties (different threshold voltages and different temperature gradients) to perform specialized functions. The first depletion transistor generates voltage with one temperature gradient while the second depletion transistor generates voltage with a different temperature gradient, allowing precise control of temperature characteristics in each local circuit.
2Temperature
If aspect ratios of depletion transistors are adjusted to achieve similar temperature gradients, then temperature stability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the parameter of aspect ratio for depletion transistors to control temperature gradients. By adjusting the aspect ratios (W/L) of the depletion transistors, the temperature gradients of the generated voltages are modified to be similar, which enables the differential amplifier to produce an output with flat temperature characteristics.
3Device complexity
If conventional reference voltage circuit with constant temperature gradient is used, then device complexity is reduced, but temperature characteristics become unsuitable for flat temperature stability
Solution Approach 1:
The reference voltage circuit uses a composite structure combining multiple constant voltage circuits with different temperature characteristics. The first constant voltage circuit and second constant voltage circuit are composite elements that, when combined through the differential amplifier, create a reference voltage with improved overall temperature characteristics that neither circuit could achieve alone.
Data Source
AI summary
Provided is a reference voltage circuit with improved temperature characteristics. A current based on a current flowing through a first depletion transistor whose gate and source are connected to each other is caused to flow through a third depletion transistor having the same threshold, to thereby generate a voltage between a gate and a source of the third depletion transistor. A current based on a current flowing through a second depletion transistor whose gate and source are connected to each other is caused to flow through a fourth depletion transistor having the same threshold, to thereby generate a voltage between a gate and a source of the fourth depletion transistor. A reference voltage is generated based on a difference voltage of the two voltages, to thereby obtain a reference voltage having less voltage fluctuations with respect to a temperature change.