Voltage Reference Circuit Offset Compensation
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Solution Overview
Problem
Existing band-gap voltage reference circuits suffer from high variability and error due to manufacturing tolerances and temperature-dependent offset voltages, leading to increased standard deviation and variability in output voltage across different circuits and temperature ranges.
Innovation Solution
A voltage reference circuit topology that separates the generation of temperature-dependent offset and junction voltages, using a main amplifier with a built-in offset-voltage and a PN junction, allowing for independent optimization of components and reducing error by canceling out temperature variations, with a single resistor-biased PN junction providing the junction-voltage and an amplifier with a built-in offset-voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a zero voltage DC offset amplifier is used to bias the diodes, then the amplifier can operate with equal voltage levels at both input terminals, but this introduces offset error due to finite manufacturing tolerances and increases the standard deviation of the band-gap value
Solution Approach 1:
The patent converts the harmful offset error into a beneficial temperature compensation mechanism. By intentionally introducing a non-zero DC offset voltage that varies with temperature, the circuit compensates for the temperature-dependent voltage drop across the diodes, achieving temperature-independent output voltage. The offset error becomes a useful feature rather than a defect.
Solution Approach 2:
The patent changes the offset voltage parameter from zero to a non-zero value that has a specific temperature coefficient. This parameter change allows the offset voltage to track and compensate for temperature variations in the diode voltage, transforming a static zero-offset design into a dynamic temperature-compensating design.
2Ease of manufacture
If two separate diodes and resistors are used to create voltage biasing, then the circuit can generate the necessary voltage difference, but manufacturing tolerances introduce error and increase variability across different circuits
Solution Approach 1:
The patent merges the offset voltage generation function into the amplifier itself, eliminating the need for separate precision resistors and diodes for biasing. This consolidation reduces the number of components subject to manufacturing tolerances and eliminates the need for precise matching between separate components.
Solution Approach 2:
The amplifier provides its own offset voltage through its inherent characteristics rather than requiring external precision components. The amplifier's internal structure generates the necessary offset voltage, making the circuit self-sufficient and less dependent on external component precision.
3Ease of operation
If the amplifier input terminals are connected at Vout/2, then the amplifier can operate with balanced inputs, but this requires a supply voltage higher than the output voltage, increasing power consumption
Solution Approach 1:
The patent makes the input voltage levels dynamic rather than static. Instead of maintaining fixed Vout/2 levels, the input voltages vary with temperature and circuit operation, allowing the amplifier to function with a lower supply voltage while still achieving the necessary differential input conditions for proper operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a more uniform reference voltage across a wide temperature range with reduced variability between circuits, achieving a percentage voltage error reduction of approximately three times compared to traditional circuits, with a standard deviation of voltage error significantly lower.
Implementation Method 1
a PN junction, comprising: a first-junction-terminal connected to the second-resistor-terminal; and a second-junction-terminal connected to a reference terminal, wherein, the PN junction is configured, in use, to provide a junction-voltage, between the first-junction-terminal and the second-junction-terminal, wherein the junction-voltage decreases with increasing temperature
Implementation Method 2
the offset-stage is configured, in use, to provide an offset-voltage between the first-input-terminal and the second-input-terminal, wherein the offset-voltage increases with increasing temperature
Data Source
AI summary
A voltage reference circuit comprising: a main amplifier, having an output-terminal for providing a reference-voltage-output-signal, wherein the output-terminal is connected to the first-input-terminal; an offset-stage, connected to at least one of a first-input-terminal and a second-input-terminal of the main amplifier; and a PN junction. The PN junction is configured, in use, to provide a junction-voltage, between the first-junction-terminal and the second-junction-terminal, wherein the junction-voltage decreases with increasing temperature. The offset-stage is configured, in use, to provide an offset-voltage between the first-input-terminal and the second-input-terminal, wherein the offset-voltage increases with increasing temperature.