Bandgap Voltage Reference Circuit for Low Supply Operation
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Solution Overview
Problem
Conventional bandgap reference circuits require a supply voltage of at least 1.4V to generate a stable reference voltage, which is not feasible in deep submicron CMOS devices with power supplies less than 1.2V, limiting their application in low voltage scenarios.
Innovation Solution
A bandgap voltage reference circuit utilizing a divider to reduce the output reference voltage, comprising a first operational amplifier, transistors, resistors, and diodes, with current mirrors formed by the transistors to generate a reference current, and a divider coupled to the second resistor to achieve a stable output voltage at lower supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bandgap reference circuit is used to generate a stable reference voltage, then the reference voltage is insensitive to temperature and supply voltage variations, but the required supply voltage must be at least 1.4V or higher
Solution Approach 1:
The circuit is divided into two main parts: a conventional bandgap reference circuit that generates a high stable voltage (approximately 1.2V), and a voltage divider network that scales this voltage down to the desired lower reference voltage level. This segmentation allows the circuit to benefit from the temperature insensitivity of the bandgap circuit while operating at lower voltages suitable for deep submicron CMOS applications.
Solution Approach 2:
A voltage divider network acts as an intermediary between the conventional bandgap reference circuit and the final output. The divider consists of resistors and transistors that scale down the bandgap voltage to a lower level while maintaining temperature compensation. This intermediary structure enables the system to achieve both voltage stability and low operating voltage.
2Adaptability or versatility
If the supply voltage is reduced to below 1.2V for deep submicron CMOS applications, then power consumption is reduced and device compatibility is improved, but conventional bandgap reference circuits cannot be implemented
Solution Approach 1:
The reference circuit is segmented into a voltage generation stage (conventional bandgap) and a voltage scaling stage (divider network). This allows the use of well-established bandgap circuitry that can be manufactured in deep submicron CMOS processes, while the divider stage adapts the voltage to suitable levels for these low-voltage applications.
Solution Approach 2:
The circuit changes the voltage parameter from the typical 1.2V bandgap output to a lower reference voltage level (e.g., 0.6V to 0.8V) appropriate for deep submicron CMOS operations. This parameter transformation is achieved through the voltage divider while maintaining the temperature compensation characteristics.
3Use of energy by moving object
If a voltage divider is added to reduce the output reference voltage, then the circuit can operate at lower supply voltages, but the device complexity increases
Solution Approach 1:
The voltage divider network serves multiple functions: it scales down the bandgap voltage to the appropriate level, provides temperature compensation through matched transistor pairs, and establishes proper biasing conditions for the circuit. By combining these functions into a single structure, the added complexity is minimized while achieving the desired low-voltage operation.
Solution Approach 2:
The voltage divider components are merged with the bandgap reference circuit components, sharing common elements such as transistors and resistors. This integration reduces the total component count and simplifies the overall circuit structure compared to having separate voltage generation and division stages.
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
Enables the generation of a stable reference voltage insensitive to temperature across a wide range of temperatures and supply voltages as low as 1V, maintaining output stability between 593mV and 597mV from 0°C to 100°C with power supplies between 0.9V and 1.1V.
Implementation Method 1
The base-emitter voltage has a negative temperature coefficient; that is, the base-emitter voltage decreases as the temperature increases. On the other hand, the voltage difference between the base and the emitter has a positive temperature coefficient
Implementation Method 2
Vt=kT/q Where Ic is the collector current, Is is the saturation current, k is Boltzmann constant, T is temperature, q is electron charges, and Vt is the thermal voltage. Vt is about 26 mV at room temperature (∼300K)
Implementation Method 3
A bandgap voltage reference circuit utilizes a divider to reduce the output reference voltage
Implementation Method 4
A gate of the first transistor is coupled to an output end of the first operational amplifier. A drain of the first transistor is coupled to a positive input end of the first operational amplifier
Data Source
AI summary
A bandgap voltage reference circuit includes an operational amplifier, a first transistor, a second transistor, a third transistor, a first resistor, a second resistor, a first diode, a second diode, and a divider. The first transistor, the second transistor, and the third transistor form current mirrors. The reference current of the current mirrors is generated according to the first diode, the second diode, and the first resistor. The reference voltage of the voltage reference circuit is output from the first end of the second resistor. The divider is coupled to the second end of the second resistor so that the reference voltage of the voltage reference circuit can be reduced.