Bandgap Reference Circuit Using Parasitic PNPs for Lower Current

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Solution Overview

Problem

Existing bandgap voltage reference generators in CMOS technology require additional power sources and operational amplifiers, leading to increased current consumption, which is inefficient for devices like DRAMs and flash memories.

Innovation Solution

A circuit arrangement that generates a bandgap reference voltage using only two parasitic PNP bipolar substrate transistors with a reference-voltage generation module and current mirrors, eliminating the need for additional current paths and operational amplifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If additional power sources and operational amplifiers are used in bandgap voltage reference generators, then the precision and stability of reference voltage generation is improved, but current consumption increases

Engineering Contradiction:

Improveprecision of reference voltage generationVSAvoidcurrent consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts and removes the operational amplifier component from the traditional bandgap voltage reference generator circuit. By eliminating the op-amp, the circuit achieves the desired reference voltage without the additional current consumption path that the operational amplifier would create, while still maintaining precision through the parasitic bipolar transistor configuration

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes the parasitic bipolar transistors perform multiple functions simultaneously. These transistors serve both as the core bandgap voltage generation elements and as the means to achieve precise voltage reference without requiring separate operational amplifiers, thereby reducing overall current consumption while maintaining precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Stability of the object's composition

If additional current paths are added to generate bandgap reference voltage, then the stability of reference voltage is improved, but device complexity and power consumption increase

Engineering Contradiction:

Improvestability of reference voltageVSAvoidcircuit complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent merges the voltage reference generation function with the existing parasitic bipolar transistor structures already present in CMOS technology. By combining the bandgap voltage generation with the inherent transistor characteristics rather than adding separate current paths and operational amplifiers, the circuit achieves stability without increasing complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent utilizes the parasitic bipolar transistors that naturally exist in CMOS technology as the primary mechanism for generating the bandgap reference voltage. These transistors serve themselves by leveraging their inherent physical characteristics to provide stable reference voltage without requiring external operational amplifiers or additional complex circuitry

Inventive Principle:

Principle #25Self-service

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 solution reduces current consumption by approximately 33% while maintaining precision in generating the bandgap reference voltage, essential for analog and digital circuits such as DRAMs and flash memories.

Implementation Method 1

A bandgap voltage reference operates on the basis of the principle of balancing in a circuit the negative temperature coefficient of a pn junction, usually the voltage VBE on the base-emitter junction of a bipolar transistor, with the positive temperature coefficient of the thermal voltage VT

Methodology Applied

Scientific EffectBandgap voltage reference principle:

Implementation Method 2

The base-emitter voltage VBE of a bipolar transistor has a negative temperature coefficient of approximately −2.2 mV/° C. at room temperature; i.e., it is a coefficient of a CTAT (Complementary To Absolute Temperature) electrical quantity

Methodology Applied

Scientific EffectPN junction temperature coefficient:

Implementation Method 3

a bandgap voltage reference adds together two quantities, a PTAT one and a CTAT one, in particular two voltages, so as to obtain a voltage reference with zero temperature coefficient

Methodology Applied

Scientific EffectTemperature coefficient balancing:

Data Source

PatentUS11036251B2Circuit arrangement for the generation of a bandgap reference voltage

Publication Date: 2021.06.15 STMICROELECTRONICS SRL

AI summary

A circuit for generating a bandgap voltage includes a circuit module for generation of a base-emitter voltage difference formed by a pair of PNP bipolar substrate transistors which identify a first current path and a second current path. A first current mirror of an n type is connected between the first and second branches and is further connected via a resistance for adjustment of the bandgap voltage to the second bipolar transistor. A second current mirror of a p type is connected between the first and second branches, and connected so that the current mirrors repeat current of each other. In operation to generate the bandgap voltage, current flows from the supply voltage to ground only through said the first and second bipolar substrate transistors.