Voltage Generating Circuit Offset Reduction
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Solution Overview
Problem
Existing voltage generating circuits, particularly band gap reference (BGR) circuits, face challenges in reducing the influence of amplifier offset and temperature dependence, making it difficult to operate at low power supply voltages and maintain accuracy across a wide temperature range.
Innovation Solution
A voltage generating circuit design that includes a current generating section using bipolar transistors with different emitter areas and resistance elements, along with a voltage-current converting section, to reduce amplifier offset influence and temperature dependence, allowing for low power supply voltage operation and improved temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BGR circuit is used, then temperature dependence is reduced, but amplifier offset influence remains significant and power supply voltage cannot be reduced below 1V
Solution Approach 1:
The patent extracts and eliminates the amplifier component from the BGR circuit by using a direct resistor connection between the bipolar transistor bases. This removes the amplifier offset error source entirely while maintaining temperature compensation through the resistor ratio R2/R1, resolving the contradiction between temperature stability and amplifier offset influence.
Solution Approach 2:
The patent introduces a resistor (R3) as an intermediary element connected to the emitter of the first bipolar transistor. This resistor mediates the temperature compensation mechanism by creating a voltage drop that counteracts the non-linear temperature dependence of the base-emitter voltage, enabling temperature stability without requiring an amplifier.
2Use of energy by moving object
If the output voltage is reduced to enable low power supply voltage operation, then power supply voltage can be reduced to 1V or lower, but the circuit becomes more sensitive to offset and mismatching
Solution Approach 1:
By removing the amplifier from the circuit, the patent eliminates the primary source of offset error that would otherwise be amplified and affect the output voltage accuracy. This allows the circuit to operate at low power supply voltages (1V or lower) without becoming excessively sensitive to offset, as there is no amplifier to magnify such errors.
Solution Approach 2:
The patent implements a feedback mechanism through the resistor network (R1, R2, R3) that automatically compensates for voltage variations. The resistor ratios are designed to provide negative feedback that stabilizes the output voltage against offset and mismatching effects, enabling low voltage operation while maintaining precision.
3Reliability
If temperature correction is implemented using existing methods, then linear temperature dependence is reduced, but non-linear temperature dependence remains and circuit complexity increases
Solution Approach 1:
The patent applies local quality by using resistors with specific temperature coefficients and precise resistance ratios (R2/R1) tailored to compensate for the non-linear temperature characteristics of the bipolar transistor. This localized compensation approach addresses temperature dependence without requiring complex global circuit modifications, maintaining simplicity while improving reliability.
Solution Approach 2:
The patent changes the circuit parameters (resistor values and ratios) to optimize temperature compensation. By carefully selecting R1, R2, and R3 values, the circuit achieves compensation for non-linear temperature dependence through parameter optimization rather than structural complexity, resolving the contradiction between reliability and device complexity.
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
The proposed circuit effectively reduces amplifier offset influence and temperature dependence, enabling operation at low power supply voltages and maintaining voltage stability across a wide temperature range, thus addressing the limitations of existing BGR circuits.
Implementation Method 1
the temperature dependence of a base-emitter voltage of a bipolar transistor (also referred to as a bipolar junction transistor (BJT)) that is a basic component of the BGR circuit is non-linear
Implementation Method 2
a first resistance element that is disposed on the collector side of the first bipolar transistor at one end thereof and is disposed on a base side of the first bipolar transistor at the other end thereof
Data Source
AI summary
A voltage generating circuit, in which the influence of offset of an amplifier on an output voltage is reduced, has first and second bipolar transistors (Q1, Q2) having emitter terminals at the same electric potential. A base terminal of Q1 is disposed on a collector side of Q2. A first resistance element connects the collector side of Q2 with the base side of Q2; and a second resistance element (R1) connects a collector side of Q1 to R2. A third resistance element (R3) connects a base terminal of Q2 with the electric potential of the emitter terminals. An amplifier (A1) outputs a voltage based on a voltage difference between the collector sides of Q1 and Q2; and a voltage-current converting section (MP1, MP2) converts amplifier output into a current supplied to the connection node of R1 and R2. A voltage is then output on the basis of the generated current.