PTAT Current Generator Low Voltage High PSRR

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Solution Overview

Problem

Conventional PTAT current generators require high power supply voltages to achieve good power supply voltage rejection, limiting their operation under low voltage conditions while maintaining a large PSRR parameter.

Innovation Solution

A PTAT current generator design utilizing a self-biased amplifier with a folded common-gate setup and PMOS transistors, along with a feedback stage, allows operation under low power supply voltages (around 1 volt) while maintaining a high PSRR parameter, achieved through the use of PMOS transistors in common-gate configuration and a differential-input single-output amplifier architecture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a high power supply voltage is used, then the power supply voltage rejection rate (PSRR) is improved, but the device cannot operate under low voltage conditions

Engineering Contradiction:

Improvepower supply voltage rejection rateVSAvoidpower supply voltage

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the configuration parameters of the amplifier circuit, specifically using a folded common-gate setup with PMOS transistors and optimizing the feedback stage, to achieve high PSRR performance at low power supply voltages around 1 volt

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback stage with an amplifier connected between the output and input of the first stage, which equalizes voltages across the core terminals and improves power supply rejection while enabling low voltage operation

Inventive Principle:

Principle #23Feedback

2Device complexity

If conventional amplifier configurations are used, then the circuit is simple, but the voltage equalization is insufficient and input impedance is high

Engineering Contradiction:

Improveamplifier configurationVSAvoidvoltage equalization

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent divides the amplifier into distinct stages: a folded common-gate first stage with PMOS transistors and a separate feedback stage, where each stage performs specific functions to achieve precise voltage equalization across the core

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback stage acts as an intermediary mechanism that senses the output voltage and adjusts the input to equalize voltages across the core terminals, achieving precise voltage matching required for accurate PTAT current generation

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8653885B2Device for generating a reference current proportional to absolute temperature, with low power supply voltage and large power supply rejection rate

Publication Date: 2014.02.18 STMICROELECTRONICS (ROUSSET) SAS

AI summary

The device for generating a reference current proportional to absolute temperature comprises processing means connected to the terminals of a core and designed to equalize the voltages across the terminals of the core, the core being designed to then be traversed by an internal current proportional to absolute temperature, and an output module designed to deliver to an output terminal the said reference current on the basis of the said internal current; the processing means comprise a self-biased amplifier possessing at least one first stage arranged according to a folded setup and comprising first PMOS transistors arranged in a setup of the common-gate type, and a feedback stage whose input is connected to the output of the amplifier and whose output is connected to the input of the first stage as well as to at least one terminal of the core.