Low Voltage Bandgap Reference Circuit Design

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Solution Overview

Problem

There is a need for a bandgap reference circuit that can provide a low reference voltage of less than 1.2 volts, which is independent of temperature and supply voltage variations, as existing circuits struggle to maintain consistency at lower power supply voltages and smaller design dimensions.

Innovation Solution

A low voltage bandgap reference circuit is designed using bipolar junction transistors and current sources, where the output voltage is calculated as the sum of a PTAT difference voltage and the voltage across a resistor, allowing for a temperature-independent output voltage with minimal input voltage requirements, and featuring a simplified structure with fewer transistors and resistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional bandgap reference circuits are used, then temperature independence is achieved, but the reference voltage magnitude cannot be reduced below 1.2V

Engineering Contradiction:

Improvepower consumptionVSAvoidreference voltage stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the fundamental parameters of the bandgap reference circuit by using a different topology that allows the reference voltage to be scaled down. Instead of relying on the traditional 1.2V bandgap voltage, the circuit uses a configuration with operational amplifiers and transistors that can generate reference voltages as low as 100mV while maintaining temperature independence through feedback control mechanisms.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic elements including operational amplifiers with feedback loops that actively adjust and maintain the reference voltage level. This dynamic control allows the circuit to adapt to different voltage requirements while compensating for temperature variations, enabling both low voltage output and stable reference performance.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If lower power supply voltages are used, then power consumption is reduced, but maintaining reference voltage consistency becomes difficult

Engineering Contradiction:

Improvepower consumptionVSAvoidreference voltage consistency

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs feedback mechanisms through operational amplifiers that continuously monitor and adjust the reference voltage to maintain consistency. The feedback loops compensate for variations caused by low supply voltages, ensuring that the reference voltage remains stable and consistent even when operating from reduced power supplies, thus resolving the contradiction between low power consumption and voltage consistency.

Inventive Principle:

Principle #23Feedback

3Temperature

If traditional bandgap reference circuits are used, then temperature compensation is achieved, but the circuit complexity increases with more transistors and resistors

Engineering Contradiction:

Improvetemperature independenceVSAvoidcircuit structure

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The patent achieves temperature independence with reduced complexity by using operational amplifiers that perform multiple functions: voltage amplification, feedback control, and temperature compensation all in one component. This multi-functionality eliminates the need for separate compensation circuits with additional transistors and resistors, maintaining temperature independence while simplifying the overall circuit structure.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 circuit achieves a low output voltage that remains constant over a range of temperatures, with values as low as 100 mV, reducing power consumption and eliminating the need for start-up circuitry, while maintaining a lower input voltage requirement compared to prior art.

Implementation Method 1

A bandgap reference circuit relies on the predictable variation with temperature of the bandgap energy of an underlying semiconductor material (usually silicon). Some types of prior art bandgap reference circuits use the bandgap energy of silicon in bipolar junction transistors to compensate for temperature effects.

Methodology Applied

Scientific EffectTemperature-dependent voltage generation in bipolar junction transistors:

Implementation Method 2

A bandgap reference circuit relies on the predictable variation with temperature of the bandgap energy of an underlying semiconductor material (usually silicon). The energy bandgap of silicon is on the order of one and two tenths volt (1.2 V).

Methodology Applied

Scientific EffectBandgap energy variation with temperature:

Data Source

PatentUS7408400B1System and method for providing a low voltage bandgap reference circuit

Publication Date: 2008.08.05 NAT SEMICON CORP

AI summary

A system and method are disclosed for providing a low voltage bandgap reference circuit that provides a substantially constant output voltage over a range of values of temperature. For example, the bandgap reference circuit could be capable of providing output voltages that are as low as one hundred millivolts. Also, no special start-up circuitry may be required to initiate the operation of the bandgap reference circuit. The bandgap reference circuit could further require fewer transistors and fewer resistors than prior art bandgap reference circuits.