Low Voltage Reference Voltage Circuit Design
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Solution Overview
Problem
Existing circuits for generating a reference voltage require a supply voltage greater than 1 V, making them unsuitable for recent CMOS technology operating under supply voltages less than 1 V, and they struggle to produce reference voltages greater than 0.1 V independently of the supply voltage.
Innovation Solution
A circuit design comprising PMOS transistors and bipolar transistors in a current mirror configuration, with specific current sources and resistive elements, allows for the generation of a reference voltage with a supply voltage of 0.9 V, enabling reference voltages between 0.1 V and 0.8 V, and is independent of the base current gain variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circuits with MOS transistors and bipolar transistors are used to generate reference voltage, then the reference voltage can be generated with stable precision, but the supply voltage must be greater than 1 V
Solution Approach 1:
The patent changes the operating parameters of the bipolar transistor by operating it in the active region rather than saturation, and by using specific current mirror ratios and resistor values to achieve proper biasing. This allows the circuit to function correctly at supply voltages below 1V while maintaining stable reference voltage generation through controlled parameter adjustments in the transistor operating points and component ratios.
2Adaptability or versatility
If the supply voltage is reduced to less than 1 V, then the circuit becomes suitable for recent CMOS technology, but existing circuits cannot operate properly
Solution Approach 1:
The patent adjusts key parameters including the current mirror ratio between MOS transistors, the values of resistive elements, and the biasing conditions of bipolar transistors to enable proper operation at supply voltages below 1V. These parameter changes ensure that sufficient voltage headroom is maintained across all circuit components while achieving compatibility with low-voltage CMOS technology nodes.
Solution Approach 2:
The patent employs feedback mechanisms through the resistor network connected to the bases of bipolar transistors and the current mirror configuration, which automatically adjusts the operating points to maintain stable operation. This feedback ensures that the circuit remains reliable and adapts to process variations while operating at reduced supply voltages.
3Measurement precision
If existing circuits are used to generate higher reference voltages, then the reference voltage can be increased, but the supply voltage must also increase proportionally
Solution Approach 1:
The patent introduces resistive elements as intermediary components that allow the bipolar transistors to operate in the active region with proper voltage drops. These resistors act as mediators that enable the generation of higher reference voltages by creating appropriate voltage divisions and biasing conditions, decoupling the reference voltage level from direct proportionality to the supply voltage.
Data Source
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AI summary
The invention relates to a reference voltage (VOUT) generation circuit, comprising a first current source (M4) in series with a first bipolar transistor (Q8); a second current source (M5) in series with a first resistor (R8); a third current source (M6) in series with a second bipolar transistor (Q9), the third current source being in current mirror with the first current source; a second resistor (R9) between the base of the second bipolar transistor (Q9) and the connection point between the second current source and the first resistor; and a fourth current source (M7) in series with a third resistor (R10), the connection point between the fourth current source (M7) and the third resistor (R10) defining a reference voltage (VOUT) terminal.