Bandgap Voltage Reference Circuit Curvature Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bandgap voltage reference circuits require curvature correction due to non-linearity in base-emitter voltage, which is typically achieved at the expense of die area using additional amplifiers and large resistors, necessitating a solution that corrects curvature without requiring large area devices.
Innovation Solution
A bandgap voltage reference circuit is implemented with a current biasing circuit that applies a non-linear bias current to bipolar transistors operating at different collector current densities, inherently correcting the reference voltage curvature by increasing the coefficient 'c' in the base-emitter voltage equation, thereby eliminating the need for subsequent curvature correction circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If curvature correction is implemented using additional amplifiers and large resistors, then reference voltage curvature is corrected, but die area increases
Solution Approach 1:
The patent changes the temperature exponent parameter XTI from its conventional value of 3-5 to a higher value of 10-20. This parameter change in the base-emitter voltage equation inherently corrects the curvature non-linearity without requiring additional correction circuitry, thus resolving the contradiction between curvature correction and die area
Solution Approach 2:
The patent extracts and eliminates the need for additional curvature correction circuitry (amplifiers and large resistors) by incorporating the curvature correction function directly into the biasing mechanism through the modified XTI parameter, thereby reducing die area while maintaining correction accuracy
2Measurement precision
If the temperature exponent XTI is increased to 10-20, then base-emitter voltage non-linearity is reduced, but the complexity of the biasing circuit increases
Solution Approach 1:
The patent merges the curvature correction function with the existing biasing circuit by adjusting the XTI parameter, combining multiple functions (biasing and curvature correction) into a single mechanism, thereby improving linearity without significantly increasing overall circuit complexity
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 approach reduces reference voltage curvature, achieving a temperature coefficient as low as 1.4 ppm/°C, significantly improving the accuracy and efficiency of the bandgap voltage reference without increasing die area, as demonstrated by simulations across various temperature ranges.
Implementation Method 1
The base-emitter voltage of a bipolar transistor is temperature dependent and can be defined by equation (1)
Implementation Method 2
The amplifier 118 is operable as an ideal amplifier and the base currents of the first bipolar transistor 110 and the second bipolar transistor 115 are negligible
Data Source
AI summary
A bandgap voltage reference circuit with an inherent curvature correction which comprises an amplifier having an inverting terminal, a non-inverting terminal and an output terminal is described. A first and second bipolar transistor operable at different current densities are provided each of the transistors being coupled to a corresponding one of the inverting and non-inverting terminals of the amplifier such that a ΔVbe is reflected across a first load element. A current biasing circuit is provided which includes a semiconductor device coupled to each of the first and second bipolar transistors and is configured for applying a non-linear bias current to the first and second bipolar transistors for biasing thereof.