MOSFET Reference Voltage Circuit With Temperature Compensation
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Solution Overview
Problem
Existing reference voltage circuits exhibit temperature-dependent variations in generated voltage, leading to unreliable constant voltage supply, particularly in low current consumption devices like wearable electronics, due to mismatched temperature coefficients of depletion and enhancement mode MOSFETs, necessitating additional complex circuitry that increases current consumption.
Innovation Solution
Incorporating an additional depletion type MOSFET and resistors in the reference voltage circuit, configured to connect the drain of the first depletion type MOSFET to a supply potential and the gate to its source, with the gate of the second depletion type MOSFET connected to the source of the first enhancement type MOSFET, to reduce temperature coefficient of the reference voltage and minimize current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional complex circuitry is introduced to compensate for temperature-dependent variations in reference voltage, then the temperature coefficient of the reference voltage is reduced, but the current consumption of the circuit increases
Solution Approach 1:
The patent changes the parameters of existing components (depletion mode MOSFETs) to achieve compensation. By adjusting the threshold voltages and dimensions of the depletion mode MOSFETs, the circuit achieves temperature compensation without adding complex new circuitry, thereby maintaining low current consumption while improving temperature stability.
Solution Approach 2:
The circuit uses the inherent characteristics of depletion mode MOSFETs to automatically compensate for temperature variations. The depletion mode MOSFETs self-adjust their operating points based on temperature changes, providing automatic temperature compensation without requiring external control circuits or additional power consumption.
2Reliability
If additional depletion type MOSFET is added to provide current compensation, then the temperature coefficient of reference voltage is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the temperature compensation function with the existing reference voltage generation circuit by using depletion mode MOSFETs that serve dual purposes: generating reference voltage and providing temperature compensation. This integration avoids adding separate complex compensation circuits while achieving improved temperature stability.
3Reliability
If the temperature coefficient of depletion and enhancement mode MOSFETs were matched, then the reference voltage would be constant with temperature, but the manufacturing precision requirements would increase
Solution Approach 1:
Instead of requiring precise matching of temperature coefficients, the patent changes the approach by using depletion mode MOSFETs with specifically adjusted threshold voltages and dimensions. This allows achieving temperature compensation through parameter optimization rather than precise matching, reducing manufacturing precision requirements while maintaining temperature independence.
Data Source
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AI summary
A reference voltage generating circuit comprising a first depletion type metal-oxide semiconductor field-effect transistor (MOSFET), a first enhancement type MOSFET, a reference voltage output connected between the first depletion type MOSFET and the first enhancement type MOSFET, and a second depletion type MOSFET.