Reference Voltage Circuit Using Bipolar Compensation for Stable Reception
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Solution Overview
Problem
The existing reference voltage generating circuits in home bus systems are susceptible to fluctuations in supply voltage and temperature, leading to errors in data judgment due to changes in the reference voltage, which affects the receiving sensitivity of the receiver circuit.
Innovation Solution
A reference voltage generating circuit is designed using a constant current circuit with a bipolar transistor and MOS transistors, where the voltage VBE between the base and emitter of the bipolar transistor has a negative temperature characteristic, reducing fluctuations in the current and reference voltage, and a resistor is added between the emitter and ground to adjust temperature changes, allowing for stable reference voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional reference voltage generating circuit is used, then the circuit structure is simple, but the reference voltage fluctuates with supply voltage and temperature changes
Solution Approach 1:
The patent changes the physical parameters of the circuit by introducing bipolar transistors with negative temperature coefficients and configuring current mirrors with specific transistor ratios. These parameter changes enable the circuit to compensate for temperature drift and supply voltage variations, achieving stable reference voltage output while maintaining reasonable circuit complexity
Solution Approach 2:
The patent implements feedback mechanisms through the bipolar transistor configuration and current mirror circuits. The bipolar transistor's negative temperature characteristic provides automatic compensation for temperature-induced drift, and the current mirror configuration feeds back current information to maintain stable voltage output despite supply voltage fluctuations
2Reliability
If the reference voltage generating circuit uses temperature-compensating components, then the reference voltage stability improves, but the device complexity increases
Solution Approach 1:
The patent utilizes the inherent negative temperature coefficient of bipolar transistors as a built-in compensation mechanism. By configuring the bipolar transistor in specific circuit arrangements with MOS transistors, the circuit automatically compensates for temperature effects without requiring external temperature sensors or complex compensation networks
Solution Approach 2:
The bipolar transistor serves multiple functions simultaneously: it acts as a current source, provides temperature compensation, and stabilizes the reference voltage. This multi-functionality reduces the need for separate compensation components, thereby limiting the increase in device complexity while achieving improved voltage stability
3Measurement precision
If the receiver circuit uses a stable reference voltage, then the data judgment accuracy improves, but the circuit becomes more sensitive to supply voltage fluctuations
Solution Approach 1:
The current mirror configuration creates a feedback mechanism where changes in supply voltage are automatically compensated. When supply voltage fluctuates, the bipolar transistor and current mirror adjust the current flow to maintain a stable voltage drop across the sensing resistor, thereby stabilizing the reference voltage despite supply variations
Solution Approach 2:
The patent introduces an intermediary element - the bipolar transistor with negative temperature coefficient - that mediates between the supply voltage and the reference voltage output. This intermediary absorbs the harmful effects of supply voltage fluctuations and temperature changes, transmitting only the stable reference signal to the comparator
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 configuration reduces the dependency on supply voltage and temperature, enhancing the receiving sensitivity and accuracy of the receiver circuit by stabilizing the reference voltage, thereby reducing errors in data judgment.
Implementation Method 1
the bipolar transistor's negative temperature characteristic helps stabilize the current and reduce temperature-induced fluctuations
Implementation Method 2
a current mirror configuration for voltage conversion
Data Source
AI summary
Disclosed is a reference voltage generating circuit including a constant current circuit which comprises: a first resistive element and a bipolar transistor connected in series between a supply voltage terminal and a constant potential point; a first MOS transistor having a gate connected to a node connecting the first resistive element with the bipolar transistor; a second resistive element connected in series between a source of the first MOS transistor and the constant potential point; a second MOS transistor connected between a drain of the first MOS transistor and the supply voltage terminal; and a third MOS transistor forming a current mirror in conjunction with the second MOS transistor, wherein a constant current generated by the constant current circuit or a current proportional to the generated constant current is converted to a voltage as a reference voltage.