PTAT Circuit Single Biasing Current Mismatch Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing PTAT circuits used in temperature sensors and voltage references suffer from mismatch issues due to the use of multiple current sources for biasing bipolar transistors, leading to performance variability and noise sensitivity.
Innovation Solution
A PTAT circuit design that employs a single biasing current distributed across multiple arms, utilizing bipolar transistors with specific emitter area ratios and configurations to minimize mismatch and noise, thereby generating a temperature-dependent output voltage with reduced sensitivity to component variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple current sources are used to bias bipolar transistors in PTAT circuits, then the circuit can achieve proper biasing and operation, but mismatch arises leading to performance variability and noise sensitivity
Solution Approach 1:
The patent combines multiple current sources into a single current source that biases all bipolar transistors in the PTAT circuit. This single current source is distributed to multiple arms through current mirrors, eliminating the mismatch problems associated with multiple independent current sources while maintaining proper biasing of all transistors.
Solution Approach 2:
The single current source serves multiple functions by biasing multiple bipolar transistors across different arms of the circuit. Through current mirror arrangements, this universal current source provides the necessary bias current to all transistors, reducing component count and improving matching.
2Reliability
If multiple current sources are used for biasing, then each transistor can be properly biased, but noise sensitivity increases due to mismatch
Solution Approach 1:
By merging multiple current sources into a single current source, the patent eliminates the mismatch-induced noise that would arise from independent current sources. The unified current source ensures consistent biasing across all transistors, reducing noise sensitivity.
3Manufacturing precision
If a single biasing current is used, then mismatch is avoided, but the circuit design becomes more challenging
Solution Approach 1:
The patent segments the single biasing current into multiple distributed currents using current mirrors. This allows the single current source to effectively bias multiple arms of the circuit while maintaining matching, as each arm receives a replicated portion of the original current.
Solution Approach 2:
Current mirrors serve as intermediaries that distribute the single biasing current to multiple transistors. These intermediaries ensure that the original current signal is replicated accurately across different parts of the circuit, maintaining precision while enabling extended 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 solution provides a stable, low-noise, and highly consistent PTAT voltage output with minimal variability and high power supply rejection ratio, effectively addressing mismatch and noise issues in PTAT circuits.
Implementation Method 1
A voltage which is proportional to absolute temperature (PTAT) may be obtained from the base-emitter voltage difference of two bipolar transistors operating at different collector current densities
Implementation Method 2
the circuit elements of a first arm can compensate for performance of circuit elements in a second arm such that a self-compensating circuit is provided
Data Source
AI summary
A proportional to absolute temperature, PTAT, circuit is provided. By judiciously combining circuit elements it is possible to generate a voltage at an output node of the circuit that is temperature dependent. Such a PTAT circuit can be used as a temperature sensor or can be combined with other temperature dependent circuits to provide a voltage reference.